diff --git a/packages/react-native/Libraries/Blob/RCTBlobCollector.h b/packages/react-native/Libraries/Blob/RCTBlobCollector.h
index 4d0166aab7db94..6fbf41c33ffc04 100644
--- a/packages/react-native/Libraries/Blob/RCTBlobCollector.h
+++ b/packages/react-native/Libraries/Blob/RCTBlobCollector.h
@@ -9,8 +9,7 @@
 
 @class RCTBlobManager;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JSI_EXPORT RCTBlobCollector : public jsi::HostObject {
  public:
@@ -24,5 +23,4 @@ class JSI_EXPORT RCTBlobCollector : public jsi::HostObject {
   RCTBlobManager *blobManager_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/Libraries/Blob/RCTBlobCollector.mm b/packages/react-native/Libraries/Blob/RCTBlobCollector.mm
index 60053c3a140351..c9afc78057c955 100644
--- a/packages/react-native/Libraries/Blob/RCTBlobCollector.mm
+++ b/packages/react-native/Libraries/Blob/RCTBlobCollector.mm
@@ -10,8 +10,7 @@
 #import <React/RCTBlobManager.h>
 #import <React/RCTBridge+Private.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 RCTBlobCollector::RCTBlobCollector(RCTBlobManager *blobManager, const std::string &blobId)
     : blobId_(blobId), blobManager_(blobManager)
@@ -52,5 +51,4 @@
               queue:RCTJSThread];
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/Libraries/Image/RCTImageURLLoaderWithAttribution.h b/packages/react-native/Libraries/Image/RCTImageURLLoaderWithAttribution.h
index c512736e106501..87b59f0843c6cf 100644
--- a/packages/react-native/Libraries/Image/RCTImageURLLoaderWithAttribution.h
+++ b/packages/react-native/Libraries/Image/RCTImageURLLoaderWithAttribution.h
@@ -11,8 +11,7 @@
 
 // TODO (T61325135): Remove C++ checks
 #ifdef __cplusplus
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct ImageURLLoaderAttribution {
   int32_t nativeViewTag = 0;
@@ -21,8 +20,7 @@ struct ImageURLLoaderAttribution {
   NSString *analyticTag;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
 #endif
 
 @interface RCTImageURLLoaderRequest : NSObject
diff --git a/packages/react-native/Libraries/TypeSafety/RCTConvertHelpers.h b/packages/react-native/Libraries/TypeSafety/RCTConvertHelpers.h
index d33f42c8ff18d8..f47ddeae42994c 100644
--- a/packages/react-native/Libraries/TypeSafety/RCTConvertHelpers.h
+++ b/packages/react-native/Libraries/TypeSafety/RCTConvertHelpers.h
@@ -13,12 +13,10 @@
 
 #import <FBLazyVector/FBLazyVector.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 template <typename T>
 using LazyVector = FB::LazyVector<T, id>;
-}
-}
+} // namespace facebook::react
 
 template <typename ContainerT>
 NSArray *RCTConvertVecToArray(const ContainerT &vec, id (^convertor)(typename ContainerT::value_type element))
diff --git a/packages/react-native/Libraries/TypeSafety/RCTTypedModuleConstants.h b/packages/react-native/Libraries/TypeSafety/RCTTypedModuleConstants.h
index a787b6788ebc5d..d6a71e57ac9510 100644
--- a/packages/react-native/Libraries/TypeSafety/RCTTypedModuleConstants.h
+++ b/packages/react-native/Libraries/TypeSafety/RCTTypedModuleConstants.h
@@ -30,8 +30,7 @@
 
 @end
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 // Objective-C doesn't allow arbitrary types in its lightweight generics, only object and block types. We can work
 // around that by having the struct type we care about be a block-argument. The block never exists at runtime.
@@ -45,5 +44,4 @@ ModuleConstants<T> typedConstants(typename T::Builder::Input &&value)
   return [_RCTTypedModuleConstants newWithUnsafeDictionary:builder.buildUnsafeRawValue()];
 }
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/Base/RCTManagedPointer.h b/packages/react-native/React/Base/RCTManagedPointer.h
index ff444d27e711ee..0579ae578801e3 100644
--- a/packages/react-native/React/Base/RCTManagedPointer.h
+++ b/packages/react-native/React/Base/RCTManagedPointer.h
@@ -24,8 +24,7 @@
 
 @end
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 template <typename T, typename P>
 RCTManagedPointer *managedPointer(P initializer)
@@ -34,7 +33,6 @@ RCTManagedPointer *managedPointer(P initializer)
   return [[RCTManagedPointer alloc] initWithPointer:std::move(ptr)];
 }
 
-}
-}
+} // namespace facebook::react
 
 #endif
diff --git a/packages/react-native/React/CxxBridge/JSCExecutorFactory.h b/packages/react-native/React/CxxBridge/JSCExecutorFactory.h
index 17b64037c72ef5..902b44e7049645 100644
--- a/packages/react-native/React/CxxBridge/JSCExecutorFactory.h
+++ b/packages/react-native/React/CxxBridge/JSCExecutorFactory.h
@@ -9,8 +9,7 @@
 
 #include <jsireact/JSIExecutor.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JSCExecutorFactory : public JSExecutorFactory {
  public:
@@ -25,5 +24,4 @@ class JSCExecutorFactory : public JSExecutorFactory {
   JSIExecutor::RuntimeInstaller runtimeInstaller_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/JSCExecutorFactory.mm b/packages/react-native/React/CxxBridge/JSCExecutorFactory.mm
index 78584cd4e6c121..6173ae5ccffac4 100644
--- a/packages/react-native/React/CxxBridge/JSCExecutorFactory.mm
+++ b/packages/react-native/React/CxxBridge/JSCExecutorFactory.mm
@@ -11,8 +11,7 @@
 
 #import <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 std::unique_ptr<JSExecutor> JSCExecutorFactory::createJSExecutor(
     std::shared_ptr<ExecutorDelegate> delegate,
@@ -22,5 +21,4 @@
       facebook::jsc::makeJSCRuntime(), delegate, JSIExecutor::defaultTimeoutInvoker, runtimeInstaller_);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/NSDataBigString.h b/packages/react-native/React/CxxBridge/NSDataBigString.h
index c7f5ae7f61eac4..b8c571f8182607 100644
--- a/packages/react-native/React/CxxBridge/NSDataBigString.h
+++ b/packages/react-native/React/CxxBridge/NSDataBigString.h
@@ -9,8 +9,7 @@
 
 #include <cxxreact/JSBigString.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class NSDataBigString : public JSBigString {
  public:
@@ -38,5 +37,4 @@ class NSDataBigString : public JSBigString {
   size_t m_length;
 };
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/NSDataBigString.mm b/packages/react-native/React/CxxBridge/NSDataBigString.mm
index 5708fa78a24306..620d97ecf3b0a8 100644
--- a/packages/react-native/React/CxxBridge/NSDataBigString.mm
+++ b/packages/react-native/React/CxxBridge/NSDataBigString.mm
@@ -7,8 +7,7 @@
 
 #import "NSDataBigString.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 static NSData *ensureNullTerminated(NSData *source)
 {
@@ -39,5 +38,4 @@
   m_data = ensureNullTerminated(data);
 }
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/RCTCxxBridgeDelegate.h b/packages/react-native/React/CxxBridge/RCTCxxBridgeDelegate.h
index 0285b70f217ee8..e2d48db4548d57 100644
--- a/packages/react-native/React/CxxBridge/RCTCxxBridgeDelegate.h
+++ b/packages/react-native/React/CxxBridge/RCTCxxBridgeDelegate.h
@@ -9,13 +9,11 @@
 
 #import <React/RCTBridgeDelegate.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JSExecutorFactory;
 
-}
-}
+} // namespace facebook::react
 
 // This is a separate class so non-C++ implementations don't need to
 // take a C++ dependency.
diff --git a/packages/react-native/React/CxxBridge/RCTJSIExecutorRuntimeInstaller.h b/packages/react-native/React/CxxBridge/RCTJSIExecutorRuntimeInstaller.h
index 2a40f8316ba2d4..a258102a21fff0 100644
--- a/packages/react-native/React/CxxBridge/RCTJSIExecutorRuntimeInstaller.h
+++ b/packages/react-native/React/CxxBridge/RCTJSIExecutorRuntimeInstaller.h
@@ -9,8 +9,7 @@
 
 #include <jsireact/JSIExecutor.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * Creates a lambda used to bind a JSIRuntime in the context of
@@ -19,5 +18,4 @@ namespace react {
 JSIExecutor::RuntimeInstaller RCTJSIExecutorRuntimeInstaller(
     JSIExecutor::RuntimeInstaller runtimeInstallerToWrap);
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/RCTJSIExecutorRuntimeInstaller.mm b/packages/react-native/React/CxxBridge/RCTJSIExecutorRuntimeInstaller.mm
index 0372d4190167d8..5212cdd47af90c 100644
--- a/packages/react-native/React/CxxBridge/RCTJSIExecutorRuntimeInstaller.mm
+++ b/packages/react-native/React/CxxBridge/RCTJSIExecutorRuntimeInstaller.mm
@@ -10,8 +10,7 @@
 #import <React/RCTLog.h>
 #include <chrono>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 JSIExecutor::RuntimeInstaller RCTJSIExecutorRuntimeInstaller(JSIExecutor::RuntimeInstaller runtimeInstallerToWrap)
 {
@@ -29,5 +28,4 @@
   };
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/RCTMessageThread.h b/packages/react-native/React/CxxBridge/RCTMessageThread.h
index c68fc281a405ce..cbd85025c9f8e4 100644
--- a/packages/react-native/React/CxxBridge/RCTMessageThread.h
+++ b/packages/react-native/React/CxxBridge/RCTMessageThread.h
@@ -13,8 +13,7 @@
 #import <React/RCTJavaScriptExecutor.h>
 #import <cxxreact/MessageQueueThread.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class RCTMessageThread : public MessageQueueThread,
                          public std::enable_shared_from_this<RCTMessageThread> {
@@ -36,5 +35,4 @@ class RCTMessageThread : public MessageQueueThread,
   std::atomic_bool m_shutdown;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/RCTMessageThread.mm b/packages/react-native/React/CxxBridge/RCTMessageThread.mm
index 48b2a604e7ea00..d234aaaa8cfd43 100644
--- a/packages/react-native/React/CxxBridge/RCTMessageThread.mm
+++ b/packages/react-native/React/CxxBridge/RCTMessageThread.mm
@@ -20,8 +20,7 @@
 // particular, the sync functions are only used for bridge setup and
 // teardown, and quitSynchronous is guaranteed to be called.
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 RCTMessageThread::RCTMessageThread(NSRunLoop *runLoop, RCTJavaScriptCompleteBlock errorBlock)
     : m_cfRunLoop([runLoop getCFRunLoop]), m_errorBlock(errorBlock), m_shutdown(false)
@@ -110,5 +109,4 @@
   CFRetain(m_cfRunLoop);
 }
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/RCTObjcExecutor.h b/packages/react-native/React/CxxBridge/RCTObjcExecutor.h
index 9cba372d4b0fae..87ad0858f505d0 100644
--- a/packages/react-native/React/CxxBridge/RCTObjcExecutor.h
+++ b/packages/react-native/React/CxxBridge/RCTObjcExecutor.h
@@ -12,8 +12,7 @@
 #import <React/RCTJavaScriptExecutor.h>
 #import <cxxreact/JSExecutor.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class RCTObjcExecutorFactory : public JSExecutorFactory {
  public:
@@ -29,5 +28,4 @@ class RCTObjcExecutorFactory : public JSExecutorFactory {
   RCTJavaScriptCompleteBlock m_errorBlock;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxBridge/RCTObjcExecutor.mm b/packages/react-native/React/CxxBridge/RCTObjcExecutor.mm
index df22d637bde3e6..0aa453803cf79b 100644
--- a/packages/react-native/React/CxxBridge/RCTObjcExecutor.mm
+++ b/packages/react-native/React/CxxBridge/RCTObjcExecutor.mm
@@ -20,8 +20,7 @@
 #import <cxxreact/RAMBundleRegistry.h>
 #import <folly/json.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -144,5 +143,4 @@ virtual void setGlobalVariable(std::string propName, std::unique_ptr<const JSBig
   return std::unique_ptr<JSExecutor>(new RCTObjcExecutor(m_jse, m_errorBlock, jsQueue, delegate));
 }
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxLogUtils/RCTDefaultCxxLogFunction.h b/packages/react-native/React/CxxLogUtils/RCTDefaultCxxLogFunction.h
index 2c745d5e7eded2..36a2abad2429f9 100644
--- a/packages/react-native/React/CxxLogUtils/RCTDefaultCxxLogFunction.h
+++ b/packages/react-native/React/CxxLogUtils/RCTDefaultCxxLogFunction.h
@@ -9,10 +9,8 @@
 
 #import <logger/react_native_log.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void RCTDefaultCxxLogFunction(ReactNativeLogLevel level, const char *message);
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxLogUtils/RCTDefaultCxxLogFunction.mm b/packages/react-native/React/CxxLogUtils/RCTDefaultCxxLogFunction.mm
index 449c7b3b3a37fb..a9f172cb344c2d 100644
--- a/packages/react-native/React/CxxLogUtils/RCTDefaultCxxLogFunction.mm
+++ b/packages/react-native/React/CxxLogUtils/RCTDefaultCxxLogFunction.mm
@@ -9,8 +9,7 @@
 #import <React/RCTLog.h>
 #import <glog/logging.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void RCTDefaultCxxLogFunction(ReactNativeLogLevel level, const char *message)
 {
@@ -35,5 +34,4 @@ void RCTDefaultCxxLogFunction(ReactNativeLogLevel level, const char *message)
   }
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxModule/DispatchMessageQueueThread.h b/packages/react-native/React/CxxModule/DispatchMessageQueueThread.h
index 76eaa15fd975b9..a8b755bd52c54e 100644
--- a/packages/react-native/React/CxxModule/DispatchMessageQueueThread.h
+++ b/packages/react-native/React/CxxModule/DispatchMessageQueueThread.h
@@ -10,8 +10,7 @@
 #include <React/RCTLog.h>
 #include <cxxreact/MessageQueueThread.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 // RCTNativeModule arranges for native methods to be invoked on a queue which
 // is not the JS thread.  C++ modules don't use RCTNativeModule, so this little
@@ -43,5 +42,4 @@ class DispatchMessageQueueThread : public MessageQueueThread {
   RCTModuleData *moduleData_;
 };
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxModule/RCTCxxModule.h b/packages/react-native/React/CxxModule/RCTCxxModule.h
index 75d95a30901d97..093aafee890bfe 100644
--- a/packages/react-native/React/CxxModule/RCTCxxModule.h
+++ b/packages/react-native/React/CxxModule/RCTCxxModule.h
@@ -11,13 +11,9 @@
 
 #import <React/RCTBridgeModule.h>
 
-namespace facebook {
-namespace xplat {
-namespace module {
+namespace facebook::xplat::module {
 class CxxModule;
-}
-}
-}
+} // namespace facebook::react::module
 
 /**
  * Subclass RCTCxxModule to use cross-platform CxxModule on iOS.
diff --git a/packages/react-native/React/CxxModule/RCTCxxUtils.h b/packages/react-native/React/CxxModule/RCTCxxUtils.h
index cc1454f07601ff..b4411088e19f5c 100644
--- a/packages/react-native/React/CxxModule/RCTCxxUtils.h
+++ b/packages/react-native/React/CxxModule/RCTCxxUtils.h
@@ -13,8 +13,7 @@
 @class RCTBridge;
 @class RCTModuleData;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 class NativeModule;
@@ -25,5 +24,4 @@ createNativeModules(NSArray<RCTModuleData *> *modules, RCTBridge *bridge, const
 NSError *tryAndReturnError(const std::function<void()> &func);
 NSString *deriveSourceURL(NSURL *url);
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxModule/RCTCxxUtils.mm b/packages/react-native/React/CxxModule/RCTCxxUtils.mm
index 03f0ad0c83d8df..efb1f1a105c53b 100644
--- a/packages/react-native/React/CxxModule/RCTCxxUtils.mm
+++ b/packages/react-native/React/CxxModule/RCTCxxUtils.mm
@@ -17,8 +17,7 @@
 #import "RCTCxxModule.h"
 #import "RCTNativeModule.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 using facebook::jsi::JSError;
 
@@ -101,5 +100,4 @@
   return sourceUrl ?: @"";
 }
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxModule/RCTNativeModule.h b/packages/react-native/React/CxxModule/RCTNativeModule.h
index a83b16dd7b79c0..730839a9b52e08 100644
--- a/packages/react-native/React/CxxModule/RCTNativeModule.h
+++ b/packages/react-native/React/CxxModule/RCTNativeModule.h
@@ -8,8 +8,7 @@
 #import <React/RCTModuleData.h>
 #import <cxxreact/NativeModule.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class RCTNativeModule : public NativeModule {
  public:
@@ -30,5 +29,4 @@ class RCTNativeModule : public NativeModule {
   RCTModuleData *m_moduleData;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxModule/RCTNativeModule.mm b/packages/react-native/React/CxxModule/RCTNativeModule.mm
index f400d6968d69ec..3f86bc87cb1c6a 100644
--- a/packages/react-native/React/CxxModule/RCTNativeModule.mm
+++ b/packages/react-native/React/CxxModule/RCTNativeModule.mm
@@ -26,8 +26,7 @@
 enum SchedulingContext { Sync, Async };
 }
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 static MethodCallResult invokeInner(
     RCTBridge *bridge,
@@ -235,5 +234,4 @@ static MethodCallResult invokeInner(
   return std::nullopt;
 }
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxUtils/RCTFollyConvert.h b/packages/react-native/React/CxxUtils/RCTFollyConvert.h
index 7a0c239539769d..7da61aa9bd55a6 100644
--- a/packages/react-native/React/CxxUtils/RCTFollyConvert.h
+++ b/packages/react-native/React/CxxUtils/RCTFollyConvert.h
@@ -9,11 +9,9 @@
 
 #include <folly/dynamic.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 folly::dynamic convertIdToFollyDynamic(id json);
 id convertFollyDynamicToId(const folly::dynamic &dyn);
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/CxxUtils/RCTFollyConvert.mm b/packages/react-native/React/CxxUtils/RCTFollyConvert.mm
index 4e881970903207..255c16422603ab 100644
--- a/packages/react-native/React/CxxUtils/RCTFollyConvert.mm
+++ b/packages/react-native/React/CxxUtils/RCTFollyConvert.mm
@@ -10,8 +10,7 @@
 #import <Foundation/Foundation.h>
 #import <objc/runtime.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 id convertFollyDynamicToId(const folly::dynamic &dyn)
 {
@@ -114,5 +113,4 @@ id convertFollyDynamicToId(const folly::dynamic &dyn)
   return nil;
 }
 
-}
-}
+} // namespace facebook::react
diff --git a/packages/react-native/React/Fabric/RCTImageResponseObserverProxy.h b/packages/react-native/React/Fabric/RCTImageResponseObserverProxy.h
index b12b3485ceb4d5..523396478ee186 100644
--- a/packages/react-native/React/Fabric/RCTImageResponseObserverProxy.h
+++ b/packages/react-native/React/Fabric/RCTImageResponseObserverProxy.h
@@ -13,8 +13,7 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class RCTImageResponseObserverProxy final : public ImageResponseObserver {
  public:
@@ -28,7 +27,6 @@ class RCTImageResponseObserverProxy final : public ImageResponseObserver {
   __weak id<RCTImageResponseDelegate> delegate_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
 
 NS_ASSUME_NONNULL_END
diff --git a/packages/react-native/React/Fabric/RCTImageResponseObserverProxy.mm b/packages/react-native/React/Fabric/RCTImageResponseObserverProxy.mm
index 609dbba9085328..d195d4fd81c8d9 100644
--- a/packages/react-native/React/Fabric/RCTImageResponseObserverProxy.mm
+++ b/packages/react-native/React/Fabric/RCTImageResponseObserverProxy.mm
@@ -12,8 +12,7 @@
 #import <react/renderer/imagemanager/ImageResponseObserver.h>
 #import <react/utils/ManagedObjectWrapper.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 RCTImageResponseObserverProxy::RCTImageResponseObserverProxy(id<RCTImageResponseDelegate> delegate)
     : delegate_(delegate)
@@ -49,5 +48,4 @@
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/Fabric/Utils/PlatformRunLoopObserver.h b/packages/react-native/React/Fabric/Utils/PlatformRunLoopObserver.h
index 98505f239aca71..2141d3943dd69a 100644
--- a/packages/react-native/React/Fabric/Utils/PlatformRunLoopObserver.h
+++ b/packages/react-native/React/Fabric/Utils/PlatformRunLoopObserver.h
@@ -12,8 +12,7 @@
 
 #include <react/utils/RunLoopObserver.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /*
  * Concrete iOS-specific implementation of `RunLoopObserver` using
@@ -50,5 +49,4 @@ class MainRunLoopObserver final : public PlatformRunLoopObserver {
       : PlatformRunLoopObserver(activities, owner, CFRunLoopGetMain()) {}
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/Fabric/Utils/PlatformRunLoopObserver.mm b/packages/react-native/React/Fabric/Utils/PlatformRunLoopObserver.mm
index 9f6268df447370..cf731e0b86aed9 100644
--- a/packages/react-native/React/Fabric/Utils/PlatformRunLoopObserver.mm
+++ b/packages/react-native/React/Fabric/Utils/PlatformRunLoopObserver.mm
@@ -9,8 +9,7 @@
 
 #import <mutex>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 static CFRunLoopActivity toCFRunLoopActivity(RunLoopObserver::Activity activity)
 {
@@ -93,5 +92,4 @@ static CFRunLoopActivity toCFRunLoopActivity(RunLoopObserver::Activity activity)
   return CFRunLoopGetCurrent() == runLoop_;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/React/Fabric/Utils/RCTIdentifierPool.h b/packages/react-native/React/Fabric/Utils/RCTIdentifierPool.h
index 92a35b79e22171..89c984e90d9dba 100644
--- a/packages/react-native/React/Fabric/Utils/RCTIdentifierPool.h
+++ b/packages/react-native/React/Fabric/Utils/RCTIdentifierPool.h
@@ -9,8 +9,7 @@
 
 #include <bitset>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 template <size_t size>
 class RCTIdentifierPool {
@@ -40,5 +39,4 @@ class RCTIdentifierPool {
   int lastIndex;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/cmake-utils/default-app-setup/OnLoad.cpp b/packages/react-native/ReactAndroid/cmake-utils/default-app-setup/OnLoad.cpp
index 5e7df8b86bc062..db1206a855a825 100644
--- a/packages/react-native/ReactAndroid/cmake-utils/default-app-setup/OnLoad.cpp
+++ b/packages/react-native/ReactAndroid/cmake-utils/default-app-setup/OnLoad.cpp
@@ -33,8 +33,7 @@
 #include <react/renderer/componentregistry/ComponentDescriptorProviderRegistry.h>
 #include <rncli.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void registerComponents(
     std::shared_ptr<ComponentDescriptorProviderRegistry const> registry) {
@@ -72,8 +71,7 @@ std::shared_ptr<TurboModule> javaModuleProvider(
   return rncli_ModuleProvider(name, params);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
 
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *) {
   return facebook::jni::initialize(vm, [] {
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/hermes/jni/JHermesInstance.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/hermes/jni/JHermesInstance.cpp
index e60ef0f74c3fae..4c04821a75e5c6 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/hermes/jni/JHermesInstance.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/hermes/jni/JHermesInstance.cpp
@@ -9,8 +9,7 @@
 
 #include <fb/fbjni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 jni::local_ref<JHermesInstance::jhybriddata> JHermesInstance::initHybrid(
     jni::alias_ref<jhybridobject>) {
@@ -28,5 +27,4 @@ std::unique_ptr<jsi::Runtime> JHermesInstance::createJSRuntime() noexcept {
   return HermesInstance::createJSRuntime();
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/hermes/jni/JHermesInstance.h b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/hermes/jni/JHermesInstance.h
index 13a427057bce82..117556998971d0 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/hermes/jni/JHermesInstance.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/hermes/jni/JHermesInstance.h
@@ -17,8 +17,7 @@
 #include <react/bridgeless/hermes/HermesInstance.h>
 #include "../../jni/JJSEngineInstance.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JHermesInstance
     : public jni::HybridClass<JHermesInstance, JJSEngineInstance> {
@@ -38,5 +37,4 @@ class JHermesInstance
   friend HybridBase;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSEngineInstance.h b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSEngineInstance.h
index ee166fb6b17e35..ba4d66cfea0c99 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSEngineInstance.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSEngineInstance.h
@@ -11,9 +11,7 @@
 #include <jni.h>
 #include <react/bridgeless/JSEngineInstance.h>
 
-namespace facebook {
-
-namespace react {
+namespace facebook::react {
 
 class JJSEngineInstance : public jni::HybridClass<JJSEngineInstance>,
                           public JSEngineInstance {
@@ -25,5 +23,4 @@ class JJSEngineInstance : public jni::HybridClass<JJSEngineInstance>,
   friend HybridBase;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSTimerExecutor.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSTimerExecutor.cpp
index 60a1ad64462ec9..ebd93d2d49b9fe 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSTimerExecutor.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSTimerExecutor.cpp
@@ -10,8 +10,7 @@
 #include <fb/fbjni.h>
 #include <jni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void JJSTimerExecutor::setTimerManager(
     std::weak_ptr<TimerManager> timerManager) {
@@ -33,5 +32,4 @@ void JJSTimerExecutor::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSTimerExecutor.h b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSTimerExecutor.h
index d5a9904c9fe1b8..3da6a77b1f8217 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSTimerExecutor.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJSTimerExecutor.h
@@ -13,8 +13,7 @@
 #include <react/bridgeless/TimerManager.h>
 #include <react/jni/WritableNativeArray.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JJSTimerExecutor : public jni::HybridClass<JJSTimerExecutor> {
  public:
@@ -35,5 +34,4 @@ class JJSTimerExecutor : public jni::HybridClass<JJSTimerExecutor> {
   std::weak_ptr<TimerManager> timerManager_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJavaTimerManager.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJavaTimerManager.cpp
index 36276e5d2a9380..638f664cc782ce 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJavaTimerManager.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJavaTimerManager.cpp
@@ -10,8 +10,7 @@
 #include <fb/fbjni.h>
 #include <jni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void JJavaTimerManager::createTimer(
     uint32_t timerID,
@@ -28,5 +27,4 @@ void JJavaTimerManager::deleteTimer(uint32_t timerID) {
   method(self(), timerID);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJavaTimerManager.h b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJavaTimerManager.h
index 3e39f04879a46a..d44cec367fc795 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJavaTimerManager.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JJavaTimerManager.h
@@ -12,8 +12,7 @@
 #include <fb/fbjni.h>
 #include <jni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct JJavaTimerManager : jni::JavaClass<JJavaTimerManager> {
   static auto constexpr kJavaDescriptor =
@@ -24,5 +23,4 @@ struct JJavaTimerManager : jni::JavaClass<JJavaTimerManager> {
   void deleteTimer(uint32_t timerID);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactExceptionManager.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactExceptionManager.cpp
index 2a8cbde9d12141..a8968d77bcc1aa 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactExceptionManager.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactExceptionManager.cpp
@@ -11,8 +11,7 @@
 #include <jni.h>
 #include <iostream>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void JReactExceptionManager::reportJsException(
     const JReadableMapBuffer::javaobject errorMapBuffer) {
@@ -24,5 +23,4 @@ void JReactExceptionManager::reportJsException(
   }
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactExceptionManager.h b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactExceptionManager.h
index 7f16ec9ca7e30f..23b4ea46b900a4 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactExceptionManager.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactExceptionManager.h
@@ -11,8 +11,7 @@
 #include <jni.h>
 #include <react/common/mapbuffer/JReadableMapBuffer.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JReactExceptionManager
     : public facebook::jni::JavaClass<JReactExceptionManager> {
@@ -23,5 +22,4 @@ class JReactExceptionManager
   void reportJsException(const JReadableMapBuffer::javaobject errorMapBuffer);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactInstance.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactInstance.cpp
index 2d1837ac9df550..d5ce7517657ac5 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactInstance.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactInstance.cpp
@@ -26,8 +26,7 @@
 #include <react/renderer/mapbuffer/MapBuffer.h>
 #include "JavaTimerRegistry.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 JReactInstance::JReactInstance(
     jni::alias_ref<JJSEngineInstance::javaobject> jsEngineInstance,
@@ -232,5 +231,4 @@ void JReactInstance::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactInstance.h b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactInstance.h
index 6604af59955b3b..61dfa4debee201 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactInstance.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JReactInstance.h
@@ -27,8 +27,7 @@
 #include "JJavaTimerManager.h"
 #include "JReactExceptionManager.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JReactInstance : public jni::HybridClass<JReactInstance> {
  public:
@@ -105,5 +104,4 @@ class JReactInstance : public jni::HybridClass<JReactInstance> {
   jni::global_ref<JBindingsInstaller::javaobject> jBindingsInstaller_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JavaTimerRegistry.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JavaTimerRegistry.cpp
index 3cbff64a6e9a49..842cade5af292f 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JavaTimerRegistry.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JavaTimerRegistry.cpp
@@ -7,8 +7,7 @@
 
 #include "JavaTimerRegistry.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 JavaTimerRegistry::JavaTimerRegistry(
     jni::global_ref<JJavaTimerManager::javaobject> javaTimerManager)
@@ -26,5 +25,4 @@ void JavaTimerRegistry::deleteTimer(uint32_t timerID) {
   javaTimerManager_->deleteTimer(timerID);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JavaTimerRegistry.h b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JavaTimerRegistry.h
index dbfd43bde72372..ae89a5296f8b5f 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JavaTimerRegistry.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/bridgeless/jni/JavaTimerRegistry.h
@@ -14,8 +14,7 @@
 
 #include "JJavaTimerManager.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * Call into JavaTimerManager.java to schedule and delete timers
@@ -36,5 +35,4 @@ class JavaTimerRegistry : public PlatformTimerRegistry {
   jni::global_ref<JJavaTimerManager::javaobject> javaTimerManager_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.cpp
index 1a9743187a31cd..a4bb58e0eb6cd3 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.cpp
@@ -37,8 +37,7 @@
 #include <react/renderer/uimanager/primitives.h>
 #include <react/utils/ContextContainer.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 jni::local_ref<Binding::jhybriddata> Binding::initHybrid(
     jni::alias_ref<jclass>) {
@@ -586,5 +585,4 @@ void Binding::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.h
index d3ba4dd4dd7f70..a1f443b1bcaa5b 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/Binding.h
@@ -22,8 +22,7 @@
 #include "EventEmitterWrapper.h"
 #include "JFabricUIManager.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class ComponentFactory;
 class EventBeatManager;
@@ -151,5 +150,4 @@ class Binding : public jni::HybridClass<Binding>,
   bool enableFabricLogs_{false};
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ComponentFactory.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ComponentFactory.cpp
index 77425a03549f70..e7ecc79aba21a1 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ComponentFactory.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ComponentFactory.cpp
@@ -13,8 +13,7 @@
 
 using namespace facebook::jsi;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 jni::local_ref<ComponentFactory::jhybriddata> ComponentFactory::initHybrid(
     jni::alias_ref<jclass>) {
@@ -27,5 +26,4 @@ void ComponentFactory::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ComponentFactory.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ComponentFactory.h
index ffbb3f7ba3aac7..b7ae67dd0e1d2a 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ComponentFactory.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ComponentFactory.h
@@ -11,8 +11,7 @@
 #include <react/renderer/componentregistry/ComponentDescriptorFactory.h>
 #include <react/renderer/componentregistry/ComponentDescriptorRegistry.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 
@@ -29,5 +28,4 @@ class ComponentFactory : public jni::HybridClass<ComponentFactory> {
   static jni::local_ref<jhybriddata> initHybrid(jni::alias_ref<jclass>);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/CoreComponentsRegistry.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/CoreComponentsRegistry.cpp
index 933e9fed2a596e..b82a561a074c05 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/CoreComponentsRegistry.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/CoreComponentsRegistry.cpp
@@ -24,8 +24,7 @@
 #include <react/renderer/components/text/TextComponentDescriptor.h>
 #include <react/renderer/components/view/ViewComponentDescriptor.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 CoreComponentsRegistry::CoreComponentsRegistry(ComponentFactory *delegate)
     : delegate_(delegate) {}
@@ -109,5 +108,4 @@ void CoreComponentsRegistry::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/CoreComponentsRegistry.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/CoreComponentsRegistry.h
index 4821ee29f7339b..a9f24c9c003b32 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/CoreComponentsRegistry.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/CoreComponentsRegistry.h
@@ -12,8 +12,7 @@
 #include <react/renderer/componentregistry/ComponentDescriptorRegistry.h>
 #include "ComponentFactory.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class CoreComponentsRegistry
     : public facebook::jni::HybridClass<CoreComponentsRegistry> {
@@ -38,5 +37,4 @@ class CoreComponentsRegistry
       ComponentFactory *delegate);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventBeatManager.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventBeatManager.cpp
index 9e9e383792e809..eeafad82499da4 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventBeatManager.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventBeatManager.cpp
@@ -9,8 +9,7 @@
 #include <fbjni/fbjni.h>
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 EventBeatManager::EventBeatManager(
     jni::alias_ref<EventBeatManager::jhybriddata> jhybridobject)
@@ -48,5 +47,4 @@ void EventBeatManager::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventBeatManager.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventBeatManager.h
index 39b2607770886d..228e4e9bbba129 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventBeatManager.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventBeatManager.h
@@ -14,8 +14,7 @@
 #include <fbjni/fbjni.h>
 #include <react/renderer/core/EventBeat.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class EventBeatManagerObserver {
  public:
@@ -63,5 +62,4 @@ class EventBeatManager : public jni::HybridClass<EventBeatManager> {
       jni::alias_ref<EventBeatManager::jhybriddata> jhybridobject);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventEmitterWrapper.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventEmitterWrapper.cpp
index 638cf9e2d92832..88e9f66d4be178 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventEmitterWrapper.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventEmitterWrapper.cpp
@@ -10,8 +10,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void EventEmitterWrapper::dispatchEvent(
     std::string eventName,
@@ -51,5 +50,4 @@ void EventEmitterWrapper::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventEmitterWrapper.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventEmitterWrapper.h
index a3834ad9357bc0..977fd13bca8439 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventEmitterWrapper.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/EventEmitterWrapper.h
@@ -11,8 +11,7 @@
 #include <react/jni/ReadableNativeMap.h>
 #include <react/renderer/core/EventEmitter.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 
@@ -35,5 +34,4 @@ class EventEmitterWrapper : public jni::HybridClass<EventEmitterWrapper> {
       int customCoalesceKey);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.cpp
index dcf8106c140839..8643140cc3b19d 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.cpp
@@ -26,8 +26,7 @@
 #include <cmath>
 #include <vector>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 constexpr static auto kReactFeatureFlagsJavaDescriptor =
     "com/facebook/react/config/ReactFeatureFlags";
@@ -959,5 +958,4 @@ void FabricMountingManager::onAllAnimationsComplete() {
   allAnimationsCompleteJNI(javaUIManager_);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.h
index 01248be957cbd1..ab9e159f6cf3e7 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/FabricMountingManager.h
@@ -15,8 +15,7 @@
 #include <react/renderer/mounting/MountingCoordinator.h>
 #include <react/renderer/uimanager/primitives.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class ReactNativeConfig;
 struct ShadowView;
@@ -68,5 +67,4 @@ class FabricMountingManager final {
       ShadowView const &newShadowView);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/JBackgroundExecutor.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/JBackgroundExecutor.cpp
index e6d4f641f5e1c4..43bb9ce15882b8 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/JBackgroundExecutor.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/JBackgroundExecutor.cpp
@@ -10,8 +10,7 @@
 #include <fbjni/NativeRunnable.h>
 #include <fbjni/fbjni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 using namespace facebook::jni;
 
@@ -26,5 +25,4 @@ BackgroundExecutor JBackgroundExecutor::create(const std::string &name) {
   };
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/JBackgroundExecutor.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/JBackgroundExecutor.h
index 50e37dacd18a85..337f9615c6e119 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/JBackgroundExecutor.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/JBackgroundExecutor.h
@@ -10,8 +10,7 @@
 #include <fbjni/fbjni.h>
 #include <react/renderer/uimanager/primitives.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JBackgroundExecutor : public jni::JavaClass<JBackgroundExecutor> {
  public:
@@ -21,5 +20,4 @@ class JBackgroundExecutor : public jni::JavaClass<JBackgroundExecutor> {
   static BackgroundExecutor create(const std::string &name);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/MountItem.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/MountItem.cpp
index 7e53343220f954..79046a0220a0b6 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/MountItem.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/MountItem.cpp
@@ -7,8 +7,7 @@
 
 #include "MountItem.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 CppMountItem CppMountItem::CreateMountItem(ShadowView const &shadowView) {
   return {CppMountItem::Type::Create, {}, {}, shadowView, -1};
@@ -62,5 +61,4 @@ CppMountItem CppMountItem::UpdateOverflowInsetMountItem(
   return {CppMountItem::Type::UpdateOverflowInset, {}, {}, shadowView, -1};
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/MountItem.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/MountItem.h
index f2e82f7a23e892..893eefdf2966ef 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/MountItem.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/MountItem.h
@@ -10,8 +10,7 @@
 #include <fbjni/fbjni.h>
 #include <react/renderer/mounting/ShadowView.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct JMountItem : public jni::JavaClass<JMountItem> {
   static constexpr auto kJavaDescriptor =
@@ -84,5 +83,4 @@ struct CppMountItem final {
   int index = {};
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ReactNativeConfigHolder.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ReactNativeConfigHolder.h
index faf602a2f00581..d6a7903cc0500e 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ReactNativeConfigHolder.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/ReactNativeConfigHolder.h
@@ -12,8 +12,7 @@
 #include <react/jni/ReadableNativeMap.h>
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * Implementation of ReactNativeConfig that wraps a FabricMobileConfig Java
@@ -33,5 +32,4 @@ class ReactNativeConfigHolder : public ReactNativeConfig {
   jni::global_ref<jobject> reactNativeConfig_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.cpp
index e79d25f55dfa17..f7301907b5b3d5 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.cpp
@@ -13,8 +13,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * Called from Java constructor through the JNI.
@@ -64,5 +63,4 @@ void StateWrapperImpl::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.h
index 92ec87e9bb2493..691a80d0642792 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.h
@@ -12,8 +12,7 @@
 #include <react/jni/ReadableNativeMap.h>
 #include <react/renderer/core/State.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 
@@ -38,5 +37,4 @@ class StateWrapperImpl : public jni::HybridClass<StateWrapperImpl> {
   static jni::local_ref<jhybriddata> initHybrid(jni::alias_ref<jclass>);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/SurfaceHandlerBinding.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/SurfaceHandlerBinding.cpp
index 63559fe3bb929a..688db9052bf214 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/SurfaceHandlerBinding.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/SurfaceHandlerBinding.cpp
@@ -8,8 +8,7 @@
 #include "SurfaceHandlerBinding.h"
 #include <react/renderer/scheduler/Scheduler.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 SurfaceHandlerBinding::SurfaceHandlerBinding(
     SurfaceId surfaceId,
@@ -113,5 +112,4 @@ void SurfaceHandlerBinding::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/SurfaceHandlerBinding.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/SurfaceHandlerBinding.h
index e067810a31a4c6..2fd2c812d9ef4d 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/SurfaceHandlerBinding.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/SurfaceHandlerBinding.h
@@ -13,8 +13,7 @@
 #include <react/jni/ReadableNativeMap.h>
 #include <react/renderer/scheduler/SurfaceHandler.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class SurfaceHandlerBinding : public jni::HybridClass<SurfaceHandlerBinding> {
  public:
@@ -63,5 +62,4 @@ class SurfaceHandlerBinding : public jni::HybridClass<SurfaceHandlerBinding> {
       jni::alias_ref<jstring> moduleName);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/viewPropConversions.h b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/viewPropConversions.h
index 1c05d7973fb8ec..19381f8d585a79 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/fabric/viewPropConversions.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/fabric/viewPropConversions.h
@@ -16,8 +16,7 @@
 
 #include <optional>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 static MapBuffer convertAccessibilityActions(
@@ -219,5 +218,4 @@ MapBuffer convertTransform(Transform const &transform) {
 }
 } // namespace
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/hermes/reactexecutor/OnLoad.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/hermes/reactexecutor/OnLoad.cpp
index d3182e95305f58..795a2ac7b9022e 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/hermes/reactexecutor/OnLoad.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/hermes/reactexecutor/OnLoad.cpp
@@ -19,8 +19,7 @@
 
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 static void hermesFatalHandler(const std::string &reason) {
   LOG(ERROR) << "Hermes Fatal: " << reason << "\n";
@@ -110,8 +109,7 @@ class HermesExecutorHolder
   using HybridBase::HybridBase;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
 
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved) {
   return facebook::jni::initialize(
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.cpp
index e3345f038be28b..043d5afcfaeb84 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.cpp
@@ -43,8 +43,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -418,5 +417,4 @@ CatalystInstanceImpl::getRuntimeScheduler() {
   return runtimeScheduler_;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.h
index cd242903faba8d..bc07691e331a68 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CatalystInstanceImpl.h
@@ -20,8 +20,7 @@
 #include "JavaModuleWrapper.h"
 #include "ModuleRegistryBuilder.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 class JavaScriptExecutorHolder;
@@ -117,5 +116,4 @@ class CatalystInstanceImpl : public jni::HybridClass<CatalystInstanceImpl> {
   jni::global_ref<JRuntimeScheduler::javaobject> runtimeScheduler_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapper.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapper.cpp
index f712545de7d316..aab1371be692a9 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapper.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapper.cpp
@@ -16,8 +16,7 @@
 using namespace facebook::jni;
 using namespace facebook::xplat::module;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 jni::local_ref<CxxModuleWrapper::javaobject> CxxModuleWrapper::makeDsoNative(
     jni::alias_ref<jclass>,
@@ -55,5 +54,4 @@ jni::local_ref<CxxModuleWrapper::javaobject> CxxModuleWrapper::makeDsoNative(
       std::unique_ptr<CxxModule>((*factory)()));
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapper.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapper.h
index 656fd8ef0a6e37..1534b51e29e19a 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapper.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapper.h
@@ -9,8 +9,7 @@
 
 #include "CxxModuleWrapperBase.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class CxxModuleWrapper
     : public jni::HybridClass<CxxModuleWrapper, CxxModuleWrapperBase> {
@@ -46,5 +45,4 @@ class CxxModuleWrapper
   std::unique_ptr<xplat::module::CxxModule> module_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapperBase.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapperBase.h
index 3b561522409b45..edb353ac586dcd 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapperBase.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxModuleWrapperBase.h
@@ -13,8 +13,7 @@
 #include <cxxreact/CxxModule.h>
 #include <fbjni/fbjni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct JNativeModule : jni::JavaClass<JNativeModule> {
   constexpr static const char *const kJavaDescriptor =
@@ -43,5 +42,4 @@ class CxxModuleWrapperBase
   virtual std::unique_ptr<xplat::module::CxxModule> getModule() = 0;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxSharedModuleWrapper.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxSharedModuleWrapper.h
index 1a06300c2e6dbb..8d6dd71f8c0928 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxSharedModuleWrapper.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/CxxSharedModuleWrapper.h
@@ -11,8 +11,7 @@
 
 #include "CxxModuleWrapperBase.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class CxxSharedModuleWrapper : public CxxModuleWrapperBase {
  public:
@@ -35,5 +34,4 @@ class CxxSharedModuleWrapper : public CxxModuleWrapperBase {
   std::shared_ptr<xplat::module::CxxModule> shared_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JCallback.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JCallback.h
index da480384d9e897..56f0a4109a8ea3 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JCallback.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JCallback.h
@@ -14,8 +14,7 @@
 
 #include "NativeArray.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 
@@ -55,5 +54,4 @@ class JCxxCallbackImpl : public jni::HybridClass<JCxxCallbackImpl, JCallback> {
   Callback callback_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JInspector.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JInspector.cpp
index 27eca48da219ed..a96bd26ab1bd8c 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JInspector.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JInspector.cpp
@@ -11,8 +11,7 @@
 
 #ifdef WITH_INSPECTOR
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -108,7 +107,6 @@ void JInspector::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
 
 #endif
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JInspector.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JInspector.h
index 4016365e589ade..b18d8ef58ee291 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JInspector.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JInspector.h
@@ -15,8 +15,7 @@
 
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JPage : public jni::JavaClass<JPage> {
  public:
@@ -75,7 +74,6 @@ class JInspector : public jni::HybridClass<JInspector> {
   IInspector *inspector_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
 
 #endif
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JMessageQueueThread.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JMessageQueueThread.cpp
index d95c28ea66b0b2..206844ec749050 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JMessageQueueThread.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JMessageQueueThread.cpp
@@ -15,8 +15,7 @@
 #include <fbjni/fbjni.h>
 #include <jsi/jsi.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 using namespace jni;
 
@@ -109,5 +108,4 @@ void JMessageQueueThread::quitSynchronous() {
   method(m_jobj);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactCxxErrorHandler.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactCxxErrorHandler.h
index 45b2799f77fdf0..0bbf90351db629 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactCxxErrorHandler.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactCxxErrorHandler.h
@@ -10,8 +10,7 @@
 #include <fbjni/fbjni.h>
 #include <string>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JReactCxxErrorHandler : public jni::JavaClass<JReactCxxErrorHandler> {
  public:
@@ -21,5 +20,4 @@ class JReactCxxErrorHandler : public jni::JavaClass<JReactCxxErrorHandler> {
   static void handleError(std::string message);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactMarker.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactMarker.cpp
index 6708d0d1ba8770..c3be1ad2b55a3f 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactMarker.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactMarker.cpp
@@ -11,8 +11,7 @@
 #include <glog/logging.h>
 #include <mutex>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void JReactMarker::setLogPerfMarkerIfNeeded() {
   static std::once_flag flag{};
@@ -110,5 +109,4 @@ double JReactMarker::getAppStartTime() {
   return meth(cls);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactMarker.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactMarker.h
index b945d5555a9631..a857ae4f3f72e1 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactMarker.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactMarker.h
@@ -12,8 +12,7 @@
 
 #include <cxxreact/ReactMarker.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JReactMarker : public facebook::jni::JavaClass<JReactMarker> {
  public:
@@ -41,5 +40,4 @@ class JReactMarker : public facebook::jni::JavaClass<JReactMarker> {
   static double getAppStartTime();
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactSoftExceptionLogger.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactSoftExceptionLogger.h
index fda4b85e3ebd62..e412d668585d5d 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactSoftExceptionLogger.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JReactSoftExceptionLogger.h
@@ -10,8 +10,7 @@
 #include <fbjni/fbjni.h>
 #include <string>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JReactSoftExceptionLogger
     : public jni::JavaClass<JReactSoftExceptionLogger> {
@@ -24,5 +23,4 @@ class JReactSoftExceptionLogger
       std::string message);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeExecutor.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeExecutor.cpp
index 70bda09416ccba..433e6ed143d127 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeExecutor.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeExecutor.cpp
@@ -7,8 +7,7 @@
 
 #include "JRuntimeExecutor.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 JRuntimeExecutor::JRuntimeExecutor(RuntimeExecutor runtimeExecutor)
     : runtimeExecutor_(runtimeExecutor) {}
@@ -17,5 +16,4 @@ RuntimeExecutor JRuntimeExecutor::get() {
   return runtimeExecutor_;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeExecutor.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeExecutor.h
index 03df73d1a446a5..b614ad1a1fecc3 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeExecutor.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeExecutor.h
@@ -10,8 +10,7 @@
 #include <ReactCommon/RuntimeExecutor.h>
 #include <fbjni/fbjni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JRuntimeExecutor : public jni::HybridClass<JRuntimeExecutor> {
  public:
@@ -26,5 +25,4 @@ class JRuntimeExecutor : public jni::HybridClass<JRuntimeExecutor> {
   RuntimeExecutor runtimeExecutor_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeScheduler.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeScheduler.cpp
index 7a9b3f8efaf9c2..587c32419752bc 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeScheduler.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeScheduler.cpp
@@ -7,8 +7,7 @@
 
 #include "JRuntimeScheduler.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 JRuntimeScheduler::JRuntimeScheduler(
     std::weak_ptr<RuntimeScheduler> runtimeScheduler)
@@ -18,5 +17,4 @@ std::weak_ptr<RuntimeScheduler> JRuntimeScheduler::get() {
   return runtimeScheduler_;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeScheduler.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeScheduler.h
index 8bc42bf9d024c3..6220ccedda3437 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeScheduler.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JRuntimeScheduler.h
@@ -10,8 +10,7 @@
 #include <fbjni/fbjni.h>
 #include <react/renderer/runtimescheduler/RuntimeScheduler.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JRuntimeScheduler : public jni::HybridClass<JRuntimeScheduler> {
  public:
@@ -26,5 +25,4 @@ class JRuntimeScheduler : public jni::HybridClass<JRuntimeScheduler> {
   std::weak_ptr<RuntimeScheduler> runtimeScheduler_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLoader.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLoader.cpp
index dc87d09bac8ff2..f37f1ce6ca02e2 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLoader.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLoader.cpp
@@ -20,8 +20,7 @@ using fbsystrace::FbSystraceSection;
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class AssetManagerString : public JSBigString {
  public:
@@ -95,5 +94,4 @@ loadScriptFromAssets(AAssetManager *manager, const std::string &assetName) {
       "' is packaged correctly for release."));
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLoader.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLoader.h
index d16f2990276c25..2c04656d85033f 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLoader.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLoader.h
@@ -13,8 +13,7 @@
 #include <cxxreact/JSExecutor.h>
 #include <fbjni/fbjni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct JAssetManager : jni::JavaClass<JAssetManager> {
   static constexpr auto kJavaDescriptor = "Landroid/content/res/AssetManager;";
@@ -30,5 +29,4 @@ std::unique_ptr<const JSBigString> loadScriptFromAssets(
     AAssetManager *assetManager,
     const std::string &assetName);
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLogging.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLogging.cpp
index cf0a293688abc9..be29b28aa10867 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLogging.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLogging.cpp
@@ -9,8 +9,7 @@
 
 #include <fb/log.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void reactAndroidLoggingHook(
     const std::string &message,
@@ -25,5 +24,4 @@ void reactAndroidLoggingHook(
       message, static_cast<android_LogPriority>(logLevel + ANDROID_LOG_DEBUG));
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLogging.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLogging.h
index 0fd115bafa3ca3..36a246782fe78b 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLogging.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JSLogging.h
@@ -10,13 +10,11 @@
 #include <android/log.h>
 #include <string>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void reactAndroidLoggingHook(
     const std::string &message,
     android_LogPriority logLevel);
 void reactAndroidLoggingHook(const std::string &message, unsigned int logLevel);
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaModuleWrapper.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaModuleWrapper.cpp
index 5cfdf7f5943c8c..c4e32b11cd67e2 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaModuleWrapper.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaModuleWrapper.cpp
@@ -26,8 +26,7 @@
 
 using facebook::xplat::module::CxxModule;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 std::string JMethodDescriptor::getSignature() const {
   static auto signature = javaClassStatic()->getField<jstring>("signature");
@@ -159,5 +158,4 @@ jni::local_ref<JReflectMethod::javaobject> JMethodDescriptor::getMethod()
   return getFieldValue(method);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaModuleWrapper.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaModuleWrapper.h
index f5bf7dcdf84590..40031cb0639f74 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaModuleWrapper.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaModuleWrapper.h
@@ -13,8 +13,7 @@
 
 #include "MethodInvoker.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 class MessageQueueThread;
@@ -85,5 +84,4 @@ class JavaNativeModule : public NativeModule {
   std::vector<std::optional<MethodInvoker>> syncMethods_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaScriptExecutorHolder.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaScriptExecutorHolder.h
index 1a4fa1435c10a8..55cbc3eb545927 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaScriptExecutorHolder.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JavaScriptExecutorHolder.h
@@ -10,8 +10,7 @@
 #include <cxxreact/JSExecutor.h>
 #include <fbjni/fbjni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JavaScriptExecutorHolder
     : public jni::HybridClass<JavaScriptExecutorHolder> {
@@ -31,5 +30,4 @@ class JavaScriptExecutorHolder
   std::shared_ptr<JSExecutorFactory> mExecutorFactory;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JniJSModulesUnbundle.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JniJSModulesUnbundle.cpp
index 40aab053c681ba..b9bb2b56c020f0 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JniJSModulesUnbundle.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JniJSModulesUnbundle.cpp
@@ -19,8 +19,7 @@ using magic_number_t = uint32_t;
 const magic_number_t MAGIC_FILE_HEADER = 0xFB0BD1E5;
 const char *MAGIC_FILE_NAME = "UNBUNDLE";
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 using asset_ptr =
     std::unique_ptr<AAsset, std::function<decltype(AAsset_close)>>;
@@ -94,5 +93,4 @@ JSModulesUnbundle::Module JniJSModulesUnbundle::getModule(
   return {sourceUrl, std::string(buffer, AAsset_getLength(asset.get()))};
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JniJSModulesUnbundle.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JniJSModulesUnbundle.h
index 71187fd99aec11..100cbe4b00f00e 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/JniJSModulesUnbundle.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/JniJSModulesUnbundle.h
@@ -12,8 +12,7 @@
 #include <android/asset_manager.h>
 #include <cxxreact/JSModulesUnbundle.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JniJSModulesUnbundle : public JSModulesUnbundle {
   /**
@@ -41,5 +40,4 @@ class JniJSModulesUnbundle : public JSModulesUnbundle {
   std::string m_moduleDirectory;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/MethodInvoker.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/MethodInvoker.cpp
index 4223a449980999..6a944e6b9a33ac 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/MethodInvoker.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/MethodInvoker.cpp
@@ -24,8 +24,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -311,5 +310,4 @@ MethodCallResult MethodInvoker::invoke(
   }
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/MethodInvoker.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/MethodInvoker.h
index f0ab0a16814434..da7cdd4ecd35bf 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/MethodInvoker.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/MethodInvoker.h
@@ -13,8 +13,7 @@
 #include <fbjni/fbjni.h>
 #include <folly/dynamic.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 
@@ -62,5 +61,4 @@ class MethodInvoker {
   bool isSync_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ModuleRegistryBuilder.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ModuleRegistryBuilder.cpp
index eeb248504aaed0..2d00a652e582bc 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ModuleRegistryBuilder.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ModuleRegistryBuilder.cpp
@@ -13,8 +13,7 @@
 
 #include <cxxreact/CxxNativeModule.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 std::string ModuleHolder::getName() const {
   static auto method = getClass()->getMethod<jstring()>("getName");
@@ -68,5 +67,4 @@ std::vector<std::unique_ptr<NativeModule>> buildNativeModuleList(
   return modules;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ModuleRegistryBuilder.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ModuleRegistryBuilder.h
index 6f837b8f3bb194..2902dd1da19420 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ModuleRegistryBuilder.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ModuleRegistryBuilder.h
@@ -14,8 +14,7 @@
 #include "CxxModuleWrapper.h"
 #include "JavaModuleWrapper.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class MessageQueueThread;
 
@@ -36,5 +35,4 @@ std::vector<std::unique_ptr<NativeModule>> buildNativeModuleList(
     jni::alias_ref<jni::JCollection<ModuleHolder::javaobject>::javaobject>
         cxxModules,
     std::shared_ptr<MessageQueueThread> moduleMessageQueue);
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeArray.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeArray.cpp
index 6d4337877e0e7b..179cd0ab82fb6f 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeArray.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeArray.cpp
@@ -11,8 +11,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void NativeArray::assertInternalType() {
   if (!array_.isArray()) {
@@ -44,5 +43,4 @@ void NativeArray::throwIfConsumed() {
   exceptions::throwIfObjectAlreadyConsumed(this, "Array already consumed");
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeArray.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeArray.h
index 1e48e742c6bfe8..08816872d641e7 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeArray.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeArray.h
@@ -12,8 +12,7 @@
 
 #include "NativeCommon.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class NativeArray : public jni::HybridClass<NativeArray> {
  public:
@@ -48,5 +47,4 @@ class NativeArray : public jni::HybridClass<NativeArray> {
   NativeArray &operator=(const NativeArray &) = delete;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeCommon.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeCommon.cpp
index 3b604bd06e7240..b7134f7276ff72 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeCommon.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeCommon.cpp
@@ -9,8 +9,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace exceptions {
 const char *gUnexpectedNativeTypeExceptionClass =
@@ -61,5 +60,4 @@ local_ref<ReadableType> ReadableType::getType(folly::dynamic::Type type) {
   }
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeCommon.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeCommon.h
index d04c3b7bd46004..cc27b94b150bc1 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeCommon.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeCommon.h
@@ -14,8 +14,7 @@
 #define RN_EXPORT __attribute__((visibility("default")))
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct ReadableType : public jni::JavaClass<ReadableType> {
   static auto constexpr kJavaDescriptor =
@@ -38,5 +37,4 @@ void throwIfObjectAlreadyConsumed(const T &t, const char *msg) {
 
 } // namespace exceptions
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeMap.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeMap.cpp
index ee581634e6d53c..31a01a1348884a 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeMap.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeMap.cpp
@@ -11,8 +11,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 local_ref<jstring> NativeMap::toString() {
   throwIfConsumed();
@@ -35,5 +34,4 @@ void NativeMap::throwIfConsumed() {
   exceptions::throwIfObjectAlreadyConsumed(this, "Map already consumed");
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeMap.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeMap.h
index 39a42b236270d5..b61e22760e54b0 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeMap.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/NativeMap.h
@@ -12,8 +12,7 @@
 
 #include "NativeCommon.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class NativeMap : public jni::HybridClass<NativeMap> {
  public:
@@ -45,5 +44,4 @@ class NativeMap : public jni::HybridClass<NativeMap> {
   NativeMap &operator=(const NativeMap &) = delete;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp
index 5dd3d1860981ab..58bd589c43d7ab 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.cpp
@@ -31,8 +31,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -93,5 +92,4 @@ extern "C" JNIEXPORT jint JNI_OnLoad(JavaVM *vm, void *reserved) {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.h
index b68b71bd204874..54c83cb1faae4b 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/OnLoad.h
@@ -9,10 +9,8 @@
 
 #include <jni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 jmethodID getLogMarkerMethod();
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ProxyExecutor.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ProxyExecutor.cpp
index 45217f71ecfb5e..bd9e98fee5821a 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ProxyExecutor.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ProxyExecutor.cpp
@@ -18,8 +18,7 @@
 
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 const auto EXECUTOR_BASECLASS = "com/facebook/react/bridge/JavaJSExecutor";
 
@@ -140,5 +139,4 @@ std::string ProxyExecutor::getDescription() {
   return "Chrome";
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ProxyExecutor.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ProxyExecutor.h
index 79d36e50f07462..4f05c0a9a2809e 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ProxyExecutor.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ProxyExecutor.h
@@ -13,8 +13,7 @@
 #include <jni.h>
 #include "OnLoad.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * This executor factory can only create a single executor instance because it
@@ -63,5 +62,4 @@ class ProxyExecutor : public JSExecutor {
   std::shared_ptr<ExecutorDelegate> m_delegate;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeArray.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeArray.cpp
index 397108b9642f81..833db513e2f849 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeArray.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeArray.cpp
@@ -11,8 +11,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 // TODO T112842309: Remove after fbjni upgraded in OSS
 void ReadableNativeArray::mapException(const std::exception &ex) {
@@ -56,5 +55,4 @@ void ReadableNativeArray::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeArray.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeArray.h
index 0242a4907be9ba..52ab38f0bafa9d 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeArray.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeArray.h
@@ -12,8 +12,7 @@
 #include "NativeCommon.h"
 #include "NativeMap.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct ReadableArray : jni::JavaClass<ReadableArray> {
   static auto constexpr kJavaDescriptor =
@@ -41,5 +40,4 @@ class ReadableNativeArray
   jni::local_ref<jni::JArrayClass<jobject>> importTypeArray();
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeMap.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeMap.cpp
index f55a92dffb928e..6a9d554b9ac4a7 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeMap.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeMap.cpp
@@ -9,8 +9,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 // TODO T112842309: Remove after fbjni upgraded in OSS
 void ReadableNativeMap::mapException(const std::exception &ex) {
@@ -134,5 +133,4 @@ void ReadableNativeMap::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeMap.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeMap.h
index bf6a44245abfb8..2513a8a6028c27 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeMap.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/ReadableNativeMap.h
@@ -16,8 +16,7 @@
 #include "NativeMap.h"
 #include "ReadableNativeArray.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct WritableNativeMap;
 
@@ -50,5 +49,4 @@ struct ReadableNativeMap : jni::HybridClass<ReadableNativeMap, NativeMap> {
   friend struct WritableNativeMap;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeArray.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeArray.cpp
index 14746a38f62e15..46f34f08d9ee76 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeArray.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeArray.cpp
@@ -11,8 +11,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 WritableNativeArray::WritableNativeArray()
     : HybridBase(folly::dynamic::array()) {}
@@ -89,5 +88,4 @@ void WritableNativeArray::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeArray.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeArray.h
index fe5d8ad2e4e493..0b1224b6fc5b53 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeArray.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeArray.h
@@ -13,8 +13,7 @@
 
 #include "ReadableNativeArray.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct ReadableNativeMap;
 
@@ -44,5 +43,4 @@ struct WritableNativeArray
   static void registerNatives();
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeMap.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeMap.cpp
index ddb0a83343731a..a787d9c6e279ea 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeMap.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeMap.cpp
@@ -9,8 +9,7 @@
 
 using namespace facebook::jni;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 WritableNativeMap::WritableNativeMap() : HybridBase(folly::dynamic::object()) {}
 
@@ -100,5 +99,4 @@ void WritableNativeMap::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeMap.h b/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeMap.h
index 093759658cb4a2..61d153f3cf9feb 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeMap.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jni/WritableNativeMap.h
@@ -14,8 +14,7 @@
 #include "ReadableNativeArray.h"
 #include "ReadableNativeMap.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct WritableMap : jni::JavaClass<WritableMap> {
   static auto constexpr kJavaDescriptor =
@@ -46,5 +45,4 @@ struct WritableNativeMap
   friend HybridBase;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/jscexecutor/OnLoad.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/jscexecutor/OnLoad.cpp
index d61e0706d7b216..fa9a1d2697e4fd 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/jscexecutor/OnLoad.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/jscexecutor/OnLoad.cpp
@@ -15,8 +15,7 @@
 
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -72,8 +71,7 @@ class JSCExecutorHolder
   using HybridBase::HybridBase;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
 
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *reserved) {
   return facebook::jni::initialize(
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/mapbuffer/react/common/mapbuffer/JReadableMapBuffer.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/mapbuffer/react/common/mapbuffer/JReadableMapBuffer.cpp
index dd5d24cfef9de8..21bf6305cecca6 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/mapbuffer/react/common/mapbuffer/JReadableMapBuffer.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/mapbuffer/react/common/mapbuffer/JReadableMapBuffer.cpp
@@ -7,8 +7,7 @@
 
 #include "JReadableMapBuffer.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 void JReadableMapBuffer::registerNatives() {
   registerHybrid({
@@ -39,5 +38,4 @@ JReadableMapBuffer::JReadableMapBuffer(MapBuffer &&map)
       (serializedData_.size() != 0) && "Error no content in map");
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/mapbuffer/react/common/mapbuffer/JReadableMapBuffer.h b/packages/react-native/ReactAndroid/src/main/jni/react/mapbuffer/react/common/mapbuffer/JReadableMapBuffer.h
index 4aae5f03e8f1a3..3db58d3bbe35bf 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/mapbuffer/react/common/mapbuffer/JReadableMapBuffer.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/mapbuffer/react/common/mapbuffer/JReadableMapBuffer.h
@@ -13,8 +13,7 @@
 
 #include <fbjni/ByteBuffer.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JReadableMapBuffer : public jni::HybridClass<JReadableMapBuffer> {
  public:
@@ -36,5 +35,4 @@ class JReadableMapBuffer : public jni::HybridClass<JReadableMapBuffer> {
   std::vector<uint8_t> serializedData_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultComponentsRegistry.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultComponentsRegistry.cpp
index 00e2cfc15ec515..8273e31777adc7 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultComponentsRegistry.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultComponentsRegistry.cpp
@@ -12,8 +12,7 @@
 #include <react/renderer/componentregistry/ComponentDescriptorProviderRegistry.h>
 #include <react/renderer/components/rncore/ComponentDescriptors.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 std::function<void(std::shared_ptr<ComponentDescriptorProviderRegistry const>)>
     DefaultComponentsRegistry::registerComponentDescriptorsFromEntryPoint{};
@@ -66,5 +65,4 @@ void DefaultComponentsRegistry::registerNatives() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultComponentsRegistry.h b/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultComponentsRegistry.h
index 921101b6aaface..748e6aeec82dd0 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultComponentsRegistry.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultComponentsRegistry.h
@@ -13,8 +13,7 @@
 #include <react/renderer/componentregistry/ComponentDescriptorRegistry.h>
 #include <react/renderer/core/ConcreteComponentDescriptor.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class DefaultComponentsRegistry
     : public facebook::jni::HybridClass<DefaultComponentsRegistry> {
@@ -43,5 +42,4 @@ class DefaultComponentsRegistry
       ComponentFactory *delegate);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultTurboModuleManagerDelegate.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultTurboModuleManagerDelegate.cpp
index 78af98677af624..182582251bfd9f 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultTurboModuleManagerDelegate.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultTurboModuleManagerDelegate.cpp
@@ -9,8 +9,7 @@
 
 #include <rncore.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 std::function<std::shared_ptr<TurboModule>(
     const std::string &,
@@ -56,5 +55,4 @@ std::shared_ptr<TurboModule> DefaultTurboModuleManagerDelegate::getTurboModule(
   return rncore_ModuleProvider(name, params);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultTurboModuleManagerDelegate.h b/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultTurboModuleManagerDelegate.h
index c6d37782d9b25f..bbfa17c44dcd2d 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultTurboModuleManagerDelegate.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/newarchdefaults/DefaultTurboModuleManagerDelegate.h
@@ -13,8 +13,7 @@
 #include <ReactCommon/TurboModuleManagerDelegate.h>
 #include <fbjni/fbjni.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class DefaultTurboModuleManagerDelegate : public jni::HybridClass<
                                               DefaultTurboModuleManagerDelegate,
@@ -49,5 +48,4 @@ class DefaultTurboModuleManagerDelegate : public jni::HybridClass<
   using HybridBase::HybridBase;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/perftests/OnLoad.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/perftests/OnLoad.cpp
index 06b828439d2bb5..35965eb017cb2a 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/perftests/OnLoad.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/perftests/OnLoad.cpp
@@ -13,8 +13,7 @@
 #include <condition_variable>
 #include <mutex>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 using facebook::jni::alias_ref;
 
@@ -207,8 +206,7 @@ static void startWatchingForLogMessage(
 
 } // namespace logwatcher
 } // namespace
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
 
 using namespace facebook::react;
 
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/reactnativeblob/BlobCollector.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/reactnativeblob/BlobCollector.cpp
index fd5e106631ca8f..7a9285653e5ca0 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/reactnativeblob/BlobCollector.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/reactnativeblob/BlobCollector.cpp
@@ -13,8 +13,7 @@
 
 using namespace facebook;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 static constexpr auto kBlobModuleJavaDescriptor =
     "com/facebook/react/modules/blob/BlobModule";
@@ -63,5 +62,4 @@ void BlobCollector::registerNatives() {
       {makeNativeMethod("nativeInstall", BlobCollector::nativeInstall)});
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/reactnativeblob/BlobCollector.h b/packages/react-native/ReactAndroid/src/main/jni/react/reactnativeblob/BlobCollector.h
index 6f0943801c35f0..d327e44a288650 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/reactnativeblob/BlobCollector.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/reactnativeblob/BlobCollector.h
@@ -10,8 +10,7 @@
 #include <fbjni/fbjni.h>
 #include <jsi/jsi.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class BlobCollector : public jni::HybridClass<BlobCollector>,
                       public jsi::HostObject {
@@ -38,5 +37,4 @@ class BlobCollector : public jni::HybridClass<BlobCollector>,
   const std::string blobId_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/reactperflogger/reactperflogger/JNativeModulePerfLogger.h b/packages/react-native/ReactAndroid/src/main/jni/react/reactperflogger/reactperflogger/JNativeModulePerfLogger.h
index 362246c7945ac7..0ae39b952a8430 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/reactperflogger/reactperflogger/JNativeModulePerfLogger.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/reactperflogger/reactperflogger/JNativeModulePerfLogger.h
@@ -11,8 +11,7 @@
 #include <reactperflogger/NativeModulePerfLogger.h>
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JNativeModulePerfLogger
     : public jni::HybridClass<JNativeModulePerfLogger> {
@@ -26,5 +25,4 @@ class JNativeModulePerfLogger
   friend HybridBase;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CallInvokerHolder.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CallInvokerHolder.cpp
index f2d610b5e0bd8e..9b44821755b9e9 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CallInvokerHolder.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CallInvokerHolder.cpp
@@ -7,8 +7,7 @@
 
 #include "CallInvokerHolder.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 CallInvokerHolder::CallInvokerHolder(std::shared_ptr<CallInvoker> callInvoker)
     : _callInvoker(callInvoker) {}
@@ -19,5 +18,4 @@ std::shared_ptr<CallInvoker> CallInvokerHolder::getCallInvoker() {
 
 void CallInvokerHolder::registerNatives() {}
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CallInvokerHolder.h b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CallInvokerHolder.h
index 5e64012dba8ae1..3e4b4f8f2a2767 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CallInvokerHolder.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CallInvokerHolder.h
@@ -11,8 +11,7 @@
 #include <fbjni/fbjni.h>
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class CallInvokerHolder : public jni::HybridClass<CallInvokerHolder> {
  public:
@@ -28,5 +27,4 @@ class CallInvokerHolder : public jni::HybridClass<CallInvokerHolder> {
   std::shared_ptr<CallInvoker> _callInvoker;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CompositeTurboModuleManagerDelegate.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CompositeTurboModuleManagerDelegate.cpp
index dedcff8592ad62..4796310bca7277 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CompositeTurboModuleManagerDelegate.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CompositeTurboModuleManagerDelegate.cpp
@@ -7,8 +7,7 @@
 
 #include "CompositeTurboModuleManagerDelegate.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 jni::local_ref<CompositeTurboModuleManagerDelegate::jhybriddata>
 CompositeTurboModuleManagerDelegate::initHybrid(jni::alias_ref<jhybridobject>) {
@@ -55,5 +54,4 @@ void CompositeTurboModuleManagerDelegate::addTurboModuleManagerDelegate(
   mDelegates_.insert(turboModuleManagerDelegate->cthis());
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CompositeTurboModuleManagerDelegate.h b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CompositeTurboModuleManagerDelegate.h
index 257d87b53b921d..46aece570b1a6d 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CompositeTurboModuleManagerDelegate.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/CompositeTurboModuleManagerDelegate.h
@@ -13,8 +13,7 @@
 #include <string>
 #include <unordered_set>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class CompositeTurboModuleManagerDelegate
     : public jni::HybridClass<
@@ -45,5 +44,4 @@ class CompositeTurboModuleManagerDelegate
           turboModuleManagerDelegate);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManager.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManager.cpp
index 840bca41145551..8b8f2c64611ff8 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManager.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManager.cpp
@@ -19,8 +19,7 @@
 
 #include "TurboModuleManager.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -334,5 +333,4 @@ void TurboModuleManager::installJSIBindings(bool shouldCreateLegacyModules) {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManager.h b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManager.h
index f8fa3b278b9fec..03a0ad387009a6 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManager.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManager.h
@@ -20,8 +20,7 @@
 #include <memory>
 #include <unordered_map>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class TurboModuleManager : public jni::HybridClass<TurboModuleManager> {
  public:
@@ -67,5 +66,4 @@ class TurboModuleManager : public jni::HybridClass<TurboModuleManager> {
   TurboModuleProviderFunctionType createLegacyModuleProvider();
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManagerDelegate.h b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManagerDelegate.h
index 8e9dcb0a8e3947..e97575cf1a4a5a 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManagerDelegate.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/turbomodule/ReactCommon/TurboModuleManagerDelegate.h
@@ -13,8 +13,7 @@
 #include <memory>
 #include <string>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class TurboModuleManagerDelegate
     : public jni::HybridClass<TurboModuleManagerDelegate> {
@@ -33,5 +32,4 @@ class TurboModuleManagerDelegate
   friend HybridBase;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/uimanager/ComponentNameResolverManager.cpp b/packages/react-native/ReactAndroid/src/main/jni/react/uimanager/ComponentNameResolverManager.cpp
index ec528b53e4ba3c..15731e44c44087 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/uimanager/ComponentNameResolverManager.cpp
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/uimanager/ComponentNameResolverManager.cpp
@@ -14,8 +14,7 @@
 
 #include <react/renderer/componentregistry/native/NativeComponentRegistryBinding.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 using namespace facebook::jni;
 
@@ -73,5 +72,4 @@ void ComponentNameResolverManager::installJSIBindings() {
   });
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactAndroid/src/main/jni/react/uimanager/ComponentNameResolverManager.h b/packages/react-native/ReactAndroid/src/main/jni/react/uimanager/ComponentNameResolverManager.h
index 33a667e961399e..db2a8fffc56187 100644
--- a/packages/react-native/ReactAndroid/src/main/jni/react/uimanager/ComponentNameResolverManager.h
+++ b/packages/react-native/ReactAndroid/src/main/jni/react/uimanager/ComponentNameResolverManager.h
@@ -13,8 +13,7 @@
 #include <react/jni/JRuntimeExecutor.h>
 #include <set>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class ComponentNameResolverManager
     : public facebook::jni::HybridClass<ComponentNameResolverManager> {
@@ -50,5 +49,4 @@ class ComponentNameResolverManager
       facebook::jni::alias_ref<jobject> componentNameResolver);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/callinvoker/ReactCommon/CallInvoker.h b/packages/react-native/ReactCommon/callinvoker/ReactCommon/CallInvoker.h
index 30996e8f83d6cc..55aa865bfad717 100644
--- a/packages/react-native/ReactCommon/callinvoker/ReactCommon/CallInvoker.h
+++ b/packages/react-native/ReactCommon/callinvoker/ReactCommon/CallInvoker.h
@@ -12,8 +12,7 @@
 
 #include "SchedulerPriority.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 using CallFunc = std::function<void()>;
 
@@ -33,5 +32,4 @@ class CallInvoker {
   virtual ~CallInvoker() {}
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/callinvoker/ReactCommon/SchedulerPriority.h b/packages/react-native/ReactCommon/callinvoker/ReactCommon/SchedulerPriority.h
index ffa14321ef8e11..6e6a0d62e579f6 100644
--- a/packages/react-native/ReactCommon/callinvoker/ReactCommon/SchedulerPriority.h
+++ b/packages/react-native/ReactCommon/callinvoker/ReactCommon/SchedulerPriority.h
@@ -9,8 +9,7 @@
 
 #include <chrono>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 enum class SchedulerPriority : int {
   ImmediatePriority = 1,
@@ -20,5 +19,4 @@ enum class SchedulerPriority : int {
   IdlePriority = 5,
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/CxxModule.h b/packages/react-native/ReactCommon/cxxreact/CxxModule.h
index a5a89f79423a40..c6af2bf9f1e0ca 100644
--- a/packages/react-native/ReactCommon/cxxreact/CxxModule.h
+++ b/packages/react-native/ReactCommon/cxxreact/CxxModule.h
@@ -16,13 +16,11 @@
 
 using namespace std::placeholders;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 
-}
-} // namespace facebook
+} // namespace facebook::react
 
 namespace facebook {
 namespace xplat {
diff --git a/packages/react-native/ReactCommon/cxxreact/CxxNativeModule.cpp b/packages/react-native/ReactCommon/cxxreact/CxxNativeModule.cpp
index ef5c5ea532b670..53959a8112ac93 100644
--- a/packages/react-native/ReactCommon/cxxreact/CxxNativeModule.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/CxxNativeModule.cpp
@@ -19,8 +19,7 @@
 #include <logger/react_native_log.h>
 
 using facebook::xplat::module::CxxModule;
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 std::function<void(folly::dynamic)> makeCallback(
     std::weak_ptr<Instance> instance,
@@ -257,5 +256,4 @@ void CxxNativeModule::lazyInit() {
   }
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/CxxNativeModule.h b/packages/react-native/ReactCommon/cxxreact/CxxNativeModule.h
index e9902132000e22..61d21cb14e00ef 100644
--- a/packages/react-native/ReactCommon/cxxreact/CxxNativeModule.h
+++ b/packages/react-native/ReactCommon/cxxreact/CxxNativeModule.h
@@ -14,8 +14,7 @@
 #define RN_EXPORT __attribute__((visibility("default")))
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class Instance;
 class MessageQueueThread;
@@ -66,5 +65,4 @@ class RN_EXPORT CxxNativeModule : public NativeModule {
   static bool shouldWarnOnUse_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/ErrorUtils.h b/packages/react-native/ReactCommon/cxxreact/ErrorUtils.h
index d9e42f7d221fc6..aaf31b6502ab23 100644
--- a/packages/react-native/ReactCommon/cxxreact/ErrorUtils.h
+++ b/packages/react-native/ReactCommon/cxxreact/ErrorUtils.h
@@ -7,8 +7,7 @@
 
 #include <jsi/jsi.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 inline static void
 handleJSError(jsi::Runtime &runtime, const jsi::JSError &error, bool isFatal) {
@@ -40,5 +39,4 @@ handleJSError(jsi::Runtime &runtime, const jsi::JSError &error, bool isFatal) {
   }
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/Instance.cpp b/packages/react-native/ReactCommon/cxxreact/Instance.cpp
index 71bb1512be2865..1dfa0e682a34b6 100644
--- a/packages/react-native/ReactCommon/cxxreact/Instance.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/Instance.cpp
@@ -30,8 +30,7 @@
 #include <mutex>
 #include <string>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 Instance::~Instance() {
   if (nativeToJsBridge_) {
@@ -292,5 +291,4 @@ void Instance::JSCallInvoker::scheduleAsync(std::function<void()> &&work) {
   }
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/Instance.h b/packages/react-native/ReactCommon/cxxreact/Instance.h
index cf20a3529e5a86..567e72fc124a84 100644
--- a/packages/react-native/ReactCommon/cxxreact/Instance.h
+++ b/packages/react-native/ReactCommon/cxxreact/Instance.h
@@ -23,8 +23,7 @@ namespace folly {
 struct dynamic;
 }
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JSBigString;
 class JSExecutorFactory;
@@ -172,5 +171,4 @@ class RN_EXPORT Instance {
       std::make_shared<JSCallInvoker>();
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSBigString.cpp b/packages/react-native/ReactCommon/cxxreact/JSBigString.cpp
index 59e117c0818e5c..436aeec9e3a8e6 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSBigString.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/JSBigString.cpp
@@ -18,8 +18,7 @@
 
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 JSBigFileString::JSBigFileString(int fd, size_t size, off_t offset /*= 0*/)
     : m_fd{-1}, m_data{nullptr} {
@@ -95,5 +94,4 @@ std::unique_ptr<const JSBigFileString> JSBigFileString::fromPath(
   return std::make_unique<const JSBigFileString>(fd, fileInfo.st_size);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSBigString.h b/packages/react-native/ReactCommon/cxxreact/JSBigString.h
index 691bb1ac3ee5bf..79fdb666e3a71d 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSBigString.h
+++ b/packages/react-native/ReactCommon/cxxreact/JSBigString.h
@@ -17,8 +17,7 @@
 #endif
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 // JSExecutor functions sometimes take large strings, on the order of
 // megabytes.  Copying these can be expensive.  Introducing a
@@ -133,5 +132,4 @@ class RN_EXPORT JSBigFileString : public JSBigString {
   mutable const char *m_data; // Pointer to the mmapped region.
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSBundleType.cpp b/packages/react-native/ReactCommon/cxxreact/JSBundleType.cpp
index 8e6f17ab00822c..b869ceacf2928d 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSBundleType.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/JSBundleType.cpp
@@ -7,8 +7,7 @@
 
 #include "JSBundleType.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 static uint32_t constexpr RAMBundleMagicNumber = 0xFB0BD1E5;
 
@@ -38,5 +37,4 @@ bool isHermesBytecodeBundle(const BundleHeader &header) {
   return header.magic64 == HermesBCBundleMagicNumber;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSBundleType.h b/packages/react-native/ReactCommon/cxxreact/JSBundleType.h
index 7a966a94b7e8f9..945e19c58ba82e 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSBundleType.h
+++ b/packages/react-native/ReactCommon/cxxreact/JSBundleType.h
@@ -15,8 +15,7 @@
 #define RN_EXPORT __attribute__((visibility("default")))
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /*
  * Scripts given to the JS Executors to run could be in any of the following
@@ -71,5 +70,4 @@ RN_EXPORT const char *stringForScriptTag(const ScriptTag &tag);
  */
 RN_EXPORT bool isHermesBytecodeBundle(const BundleHeader &header);
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSExecutor.cpp b/packages/react-native/ReactCommon/cxxreact/JSExecutor.cpp
index 7f7bfd32e99037..dbca822cf190ce 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSExecutor.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/JSExecutor.cpp
@@ -13,8 +13,7 @@
 
 #include <chrono>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 std::string JSExecutor::getSyntheticBundlePath(
     uint32_t bundleId,
@@ -35,5 +34,4 @@ double JSExecutor::performanceNow() {
   return duration / NANOSECONDS_IN_MILLISECOND;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSExecutor.h b/packages/react-native/ReactCommon/cxxreact/JSExecutor.h
index 112426a1da4144..02dbf1928b71aa 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSExecutor.h
+++ b/packages/react-native/ReactCommon/cxxreact/JSExecutor.h
@@ -17,8 +17,7 @@
 #define RN_EXPORT __attribute__((visibility("default")))
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JSBigString;
 class JSExecutor;
@@ -142,5 +141,4 @@ class RN_EXPORT JSExecutor {
   static double performanceNow();
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSIndexedRAMBundle.cpp b/packages/react-native/ReactCommon/cxxreact/JSIndexedRAMBundle.cpp
index 5be7c1b446d1bd..f1d05a06b3ba46 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSIndexedRAMBundle.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/JSIndexedRAMBundle.cpp
@@ -12,8 +12,7 @@
 #include <memory>
 #include <sstream>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 std::function<std::unique_ptr<JSModulesUnbundle>(std::string)>
 JSIndexedRAMBundle::buildFactory() {
@@ -127,5 +126,4 @@ void JSIndexedRAMBundle::readBundle(
   readBundle(buffer, bytes);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSIndexedRAMBundle.h b/packages/react-native/ReactCommon/cxxreact/JSIndexedRAMBundle.h
index a8aa34166ada38..8f5c548e916fb8 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSIndexedRAMBundle.h
+++ b/packages/react-native/ReactCommon/cxxreact/JSIndexedRAMBundle.h
@@ -17,8 +17,7 @@
 #define RN_EXPORT __attribute__((visibility("default")))
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class RN_EXPORT JSIndexedRAMBundle : public JSModulesUnbundle {
  public:
@@ -69,5 +68,4 @@ class RN_EXPORT JSIndexedRAMBundle : public JSModulesUnbundle {
   std::unique_ptr<JSBigBufferString> m_startupCode;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/JSModulesUnbundle.h b/packages/react-native/ReactCommon/cxxreact/JSModulesUnbundle.h
index 56376758292f7d..85bf46a7714f56 100644
--- a/packages/react-native/ReactCommon/cxxreact/JSModulesUnbundle.h
+++ b/packages/react-native/ReactCommon/cxxreact/JSModulesUnbundle.h
@@ -13,8 +13,7 @@
 
 #include <folly/Conv.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JSModulesUnbundle {
   /**
@@ -44,5 +43,4 @@ class JSModulesUnbundle {
   JSModulesUnbundle(const JSModulesUnbundle &) = delete;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/MessageQueueThread.h b/packages/react-native/ReactCommon/cxxreact/MessageQueueThread.h
index 3313b1a0fd0554..b31f2168731f88 100644
--- a/packages/react-native/ReactCommon/cxxreact/MessageQueueThread.h
+++ b/packages/react-native/ReactCommon/cxxreact/MessageQueueThread.h
@@ -11,8 +11,7 @@
 #include <functional>
 #include <mutex>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class MessageQueueThread {
  public:
@@ -25,5 +24,4 @@ class MessageQueueThread {
   virtual void quitSynchronous() = 0;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/MethodCall.cpp b/packages/react-native/ReactCommon/cxxreact/MethodCall.cpp
index c5e068195d3ec0..463a31ee510b52 100644
--- a/packages/react-native/ReactCommon/cxxreact/MethodCall.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/MethodCall.cpp
@@ -10,8 +10,7 @@
 #include <folly/json.h>
 #include <stdexcept>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 #define REQUEST_MODULE_IDS 0
 #define REQUEST_METHOD_IDS 1
@@ -85,5 +84,4 @@ std::vector<MethodCall> parseMethodCalls(folly::dynamic &&jsonData) {
   return methodCalls;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/MethodCall.h b/packages/react-native/ReactCommon/cxxreact/MethodCall.h
index f2fad2f025694d..4394bcb8247ea2 100644
--- a/packages/react-native/ReactCommon/cxxreact/MethodCall.h
+++ b/packages/react-native/ReactCommon/cxxreact/MethodCall.h
@@ -13,8 +13,7 @@
 
 #include <folly/dynamic.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct MethodCall {
   int moduleId;
@@ -32,5 +31,4 @@ struct MethodCall {
 /// \throws std::invalid_argument
 std::vector<MethodCall> parseMethodCalls(folly::dynamic &&calls);
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/ModuleRegistry.cpp b/packages/react-native/ReactCommon/cxxreact/ModuleRegistry.cpp
index 962a84e0bacebe..75f6a350c3669e 100644
--- a/packages/react-native/ReactCommon/cxxreact/ModuleRegistry.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/ModuleRegistry.cpp
@@ -13,8 +13,7 @@
 #include "NativeModule.h"
 #include "SystraceSection.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -236,5 +235,4 @@ MethodCallResult ModuleRegistry::callSerializableNativeHook(
       methodId, std::move(params));
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/ModuleRegistry.h b/packages/react-native/ReactCommon/cxxreact/ModuleRegistry.h
index 55d9c0b6b045b3..a9b5555d1f5bbe 100644
--- a/packages/react-native/ReactCommon/cxxreact/ModuleRegistry.h
+++ b/packages/react-native/ReactCommon/cxxreact/ModuleRegistry.h
@@ -19,8 +19,7 @@
 #define RN_EXPORT __attribute__((visibility("default")))
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class NativeModule;
 
@@ -88,5 +87,4 @@ class RN_EXPORT ModuleRegistry {
   ModuleNotFoundCallback moduleNotFoundCallback_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/NativeModule.h b/packages/react-native/ReactCommon/cxxreact/NativeModule.h
index 5fa439703e1282..211eefeb333dc1 100644
--- a/packages/react-native/ReactCommon/cxxreact/NativeModule.h
+++ b/packages/react-native/ReactCommon/cxxreact/NativeModule.h
@@ -13,8 +13,7 @@
 #include <folly/dynamic.h>
 #include <optional>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct MethodDescriptor {
   std::string name;
@@ -41,5 +40,4 @@ class NativeModule {
       folly::dynamic &&args) = 0;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/NativeToJsBridge.cpp b/packages/react-native/ReactCommon/cxxreact/NativeToJsBridge.cpp
index ce54a90dea0afd..456bfca43d583f 100644
--- a/packages/react-native/ReactCommon/cxxreact/NativeToJsBridge.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/NativeToJsBridge.cpp
@@ -32,8 +32,7 @@
 using fbsystrace::FbSystraceAsyncFlow;
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 // This class manages calls from JS to native code.
 class JsToNativeBridge : public react::ExecutorDelegate {
@@ -340,5 +339,4 @@ std::shared_ptr<CallInvoker> NativeToJsBridge::getDecoratedNativeCallInvoker(
   return std::make_shared<NativeCallInvoker>(m_delegate, nativeInvoker);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/NativeToJsBridge.h b/packages/react-native/ReactCommon/cxxreact/NativeToJsBridge.h
index b8ba6a69c331d0..13c358614e9bba 100644
--- a/packages/react-native/ReactCommon/cxxreact/NativeToJsBridge.h
+++ b/packages/react-native/ReactCommon/cxxreact/NativeToJsBridge.h
@@ -20,8 +20,7 @@ namespace folly {
 struct dynamic;
 }
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 struct InstanceCallback;
 class JsToNativeBridge;
@@ -132,5 +131,4 @@ class NativeToJsBridge {
 #endif
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/RAMBundleRegistry.cpp b/packages/react-native/ReactCommon/cxxreact/RAMBundleRegistry.cpp
index 7946334dcdb149..ff3cd6b3cde72d 100644
--- a/packages/react-native/ReactCommon/cxxreact/RAMBundleRegistry.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/RAMBundleRegistry.cpp
@@ -11,8 +11,7 @@
 
 #include <memory>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 constexpr uint32_t RAMBundleRegistry::MAIN_BUNDLE_ID;
 
@@ -74,5 +73,4 @@ JSModulesUnbundle *RAMBundleRegistry::getBundle(uint32_t bundleId) const {
   return m_bundles.at(bundleId).get();
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/RAMBundleRegistry.h b/packages/react-native/ReactCommon/cxxreact/RAMBundleRegistry.h
index d310ef1f42c139..db6931ea2d2093 100644
--- a/packages/react-native/ReactCommon/cxxreact/RAMBundleRegistry.h
+++ b/packages/react-native/ReactCommon/cxxreact/RAMBundleRegistry.h
@@ -19,8 +19,7 @@
 #define RN_EXPORT __attribute__((visibility("default")))
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class RN_EXPORT RAMBundleRegistry {
  public:
@@ -52,5 +51,4 @@ class RN_EXPORT RAMBundleRegistry {
   std::unordered_map<uint32_t, std::unique_ptr<JSModulesUnbundle>> m_bundles;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/ReactMarker.cpp b/packages/react-native/ReactCommon/cxxreact/ReactMarker.cpp
index c154fccc1cb61c..a84b8d71b3aae0 100644
--- a/packages/react-native/ReactCommon/cxxreact/ReactMarker.cpp
+++ b/packages/react-native/ReactCommon/cxxreact/ReactMarker.cpp
@@ -8,8 +8,7 @@
 #include "ReactMarker.h"
 #include <cxxreact/JSExecutor.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 namespace ReactMarker {
 
 #if __clang__
@@ -85,5 +84,4 @@ double StartupLogger::getRunJSBundleEndTime() {
 }
 
 } // namespace ReactMarker
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/ReactMarker.h b/packages/react-native/ReactCommon/cxxreact/ReactMarker.h
index e0640ae672c2d1..76b8e7a165e8dc 100644
--- a/packages/react-native/ReactCommon/cxxreact/ReactMarker.h
+++ b/packages/react-native/ReactCommon/cxxreact/ReactMarker.h
@@ -11,8 +11,7 @@
 #include <functional>
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 namespace ReactMarker {
 
 enum ReactMarkerId {
@@ -87,5 +86,4 @@ class StartupLogger {
 };
 
 } // namespace ReactMarker
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/RecoverableError.h b/packages/react-native/ReactCommon/cxxreact/RecoverableError.h
index 4ea9fa9f91ff51..3f01dd561a81fe 100644
--- a/packages/react-native/ReactCommon/cxxreact/RecoverableError.h
+++ b/packages/react-native/ReactCommon/cxxreact/RecoverableError.h
@@ -11,8 +11,7 @@
 #include <functional>
 #include <string>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * RecoverableError
@@ -46,5 +45,4 @@ struct RecoverableError : public std::exception {
   std::string m_what;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/cxxreact/SystraceSection.h b/packages/react-native/ReactCommon/cxxreact/SystraceSection.h
index 46996ff2bb74d9..f1579db8fc46c0 100644
--- a/packages/react-native/ReactCommon/cxxreact/SystraceSection.h
+++ b/packages/react-native/ReactCommon/cxxreact/SystraceSection.h
@@ -11,8 +11,7 @@
 #include <fbsystrace.h>
 #endif
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * Allow providing an fbsystrace implementation that can short-circuit out
@@ -57,5 +56,4 @@ struct DummySystraceSection {
 using SystraceSection = DummySystraceSection;
 #endif
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.cpp b/packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.cpp
index 9d68c8c5104d48..1b4f65e4eb8d2f 100644
--- a/packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.cpp
+++ b/packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.cpp
@@ -22,8 +22,7 @@
 using namespace facebook::hermes;
 using namespace facebook::jsi;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace {
 
@@ -235,5 +234,4 @@ HermesExecutor::HermesExecutor(
   jsi::addNativeTracingHooks(*runtime);
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.h b/packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.h
index d0d5352ba5450e..1be5b60e215c4a 100644
--- a/packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.h
+++ b/packages/react-native/ReactCommon/hermes/executor/HermesExecutorFactory.h
@@ -12,8 +12,7 @@
 #include <functional>
 #include <utility>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class HermesExecutorFactory : public JSExecutorFactory {
  public:
@@ -59,5 +58,4 @@ class HermesExecutor : public JSIExecutor {
   JSIScopedTimeoutInvoker timeoutInvoker_;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jserrorhandler/JsErrorHandler.cpp b/packages/react-native/ReactCommon/jserrorhandler/JsErrorHandler.cpp
index 0902e68b2b1644..8b25ff1e95b45d 100644
--- a/packages/react-native/ReactCommon/jserrorhandler/JsErrorHandler.cpp
+++ b/packages/react-native/ReactCommon/jserrorhandler/JsErrorHandler.cpp
@@ -12,8 +12,7 @@
 #include <string>
 #include <vector>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 using facebook::react::JSErrorHandlerKey;
 
@@ -103,5 +102,4 @@ void JsErrorHandler::handleJsError(const jsi::JSError &error, bool isFatal) {
   _jsErrorHandlingFunc(std::move(errorMap));
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jserrorhandler/JsErrorHandler.h b/packages/react-native/ReactCommon/jserrorhandler/JsErrorHandler.h
index d0bc25c908855b..a188169a670e1b 100644
--- a/packages/react-native/ReactCommon/jserrorhandler/JsErrorHandler.h
+++ b/packages/react-native/ReactCommon/jserrorhandler/JsErrorHandler.h
@@ -10,8 +10,7 @@
 #include <jsi/jsi.h>
 #include <react/renderer/mapbuffer/MapBuffer.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 enum JSErrorHandlerKey : uint16_t {
   kFrameFileName = 0,
@@ -37,5 +36,4 @@ class JsErrorHandler {
   JsErrorHandlingFunc _jsErrorHandlingFunc;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
index 3e72ed8e25bb80..ec882e3da73a85 100644
--- a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
+++ b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
@@ -24,8 +24,7 @@
 
 using namespace facebook::jsi;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class JSIExecutor::NativeModuleProxy : public jsi::HostObject {
  public:
@@ -579,5 +578,4 @@ void bindNativePerformanceNow(Runtime &runtime) {
              size_t count) { return Value(JSExecutor::performanceNow()); }));
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.h b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.h
index c17a052e866d90..d5101df849f93b 100644
--- a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.h
+++ b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.h
@@ -17,8 +17,7 @@
 #include <mutex>
 #include <optional>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 // A JSIScopedTimeoutInvoker is a trampoline-type function for introducing
 // timeouts. Call the TimeoutInvoker with a function to execute, the invokee.
@@ -140,5 +139,4 @@ void bindNativeLogger(jsi::Runtime &runtime, Logger logger);
 void bindNativePerformanceNow(jsi::Runtime &runtime);
 
 double performanceNow();
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSINativeModules.cpp b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSINativeModules.cpp
index de51c93dcbfb9a..15919802a43157 100644
--- a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSINativeModules.cpp
+++ b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSINativeModules.cpp
@@ -18,8 +18,7 @@
 
 using namespace facebook::jsi;
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 JSINativeModules::JSINativeModules(
     std::shared_ptr<ModuleRegistry> moduleRegistry)
@@ -103,5 +102,4 @@ std::optional<Object> JSINativeModules::createModule(
   return module;
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSINativeModules.h b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSINativeModules.h
index fd769a703b40c0..365158f620715d 100644
--- a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSINativeModules.h
+++ b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSINativeModules.h
@@ -14,8 +14,7 @@
 #include <jsi/jsi.h>
 #include <optional>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * Holds and creates JS representations of the modules in ModuleRegistry
@@ -36,5 +35,4 @@ class JSINativeModules {
       const std::string &name);
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jsinspector/InspectorInterfaces.cpp b/packages/react-native/ReactCommon/jsinspector/InspectorInterfaces.cpp
index fbd38e13e3df53..dc02471b9cd018 100644
--- a/packages/react-native/ReactCommon/jsinspector/InspectorInterfaces.cpp
+++ b/packages/react-native/ReactCommon/jsinspector/InspectorInterfaces.cpp
@@ -11,8 +11,7 @@
 #include <tuple>
 #include <unordered_map>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 // pure destructors in C++ are odd. You would think they don't want an
 // implementation, but in fact the linker requires one. Define them to be
@@ -104,5 +103,4 @@ std::unique_ptr<IInspector> makeTestInspectorInstance() {
   return std::make_unique<InspectorImpl>();
 }
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/jsinspector/InspectorInterfaces.h b/packages/react-native/ReactCommon/jsinspector/InspectorInterfaces.h
index 77fd6e1d546a10..115a56382c8fd9 100644
--- a/packages/react-native/ReactCommon/jsinspector/InspectorInterfaces.h
+++ b/packages/react-native/ReactCommon/jsinspector/InspectorInterfaces.h
@@ -24,8 +24,7 @@
 #endif // _MSC_VER
 #endif // !defined(JSINSPECTOR_EXPORT)
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class IDestructible {
  public:
@@ -90,5 +89,4 @@ extern IInspector &getInspectorInstance();
 /// should only be used in tests.
 extern std::unique_ptr<IInspector> makeTestInspectorInstance();
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/react/bridgeless/BindingsInstaller.h b/packages/react-native/ReactCommon/react/bridgeless/BindingsInstaller.h
index 3d02fd90c3accc..fc3d889a553e41 100644
--- a/packages/react-native/ReactCommon/react/bridgeless/BindingsInstaller.h
+++ b/packages/react-native/ReactCommon/react/bridgeless/BindingsInstaller.h
@@ -9,8 +9,7 @@
 
 #include <react/bridgeless/ReactInstance.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 class BindingsInstaller {
  public:
@@ -18,5 +17,5 @@ class BindingsInstaller {
     return nullptr;
   }
 };
-} // namespace react
-} // namespace facebook
+
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/reactperflogger/reactperflogger/BridgeNativeModulePerfLogger.cpp b/packages/react-native/ReactCommon/reactperflogger/reactperflogger/BridgeNativeModulePerfLogger.cpp
index 7c0da26878a1ff..616df655e099ad 100644
--- a/packages/react-native/ReactCommon/reactperflogger/reactperflogger/BridgeNativeModulePerfLogger.cpp
+++ b/packages/react-native/ReactCommon/reactperflogger/reactperflogger/BridgeNativeModulePerfLogger.cpp
@@ -7,8 +7,7 @@
 
 #include "BridgeNativeModulePerfLogger.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 namespace BridgeNativeModulePerfLogger {
 
 std::unique_ptr<NativeModulePerfLogger> g_perfLogger = nullptr;
@@ -327,5 +326,4 @@ void asyncMethodCallExecutionFail(
 }
 
 } // namespace BridgeNativeModulePerfLogger
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/reactperflogger/reactperflogger/BridgeNativeModulePerfLogger.h b/packages/react-native/ReactCommon/reactperflogger/reactperflogger/BridgeNativeModulePerfLogger.h
index c9593ec86f39c9..e1ed6d1cef8d25 100644
--- a/packages/react-native/ReactCommon/reactperflogger/reactperflogger/BridgeNativeModulePerfLogger.h
+++ b/packages/react-native/ReactCommon/reactperflogger/reactperflogger/BridgeNativeModulePerfLogger.h
@@ -9,8 +9,7 @@
 #include <memory>
 #include "NativeModulePerfLogger.h"
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 namespace BridgeNativeModulePerfLogger {
 void enableLogging(std::unique_ptr<NativeModulePerfLogger> &&logger);
@@ -109,5 +108,4 @@ void asyncMethodCallExecutionFail(
 
 } // namespace BridgeNativeModulePerfLogger
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/reactperflogger/reactperflogger/NativeModulePerfLogger.h b/packages/react-native/ReactCommon/reactperflogger/reactperflogger/NativeModulePerfLogger.h
index 2cb386b48afb56..864ddfc1d32ebd 100644
--- a/packages/react-native/ReactCommon/reactperflogger/reactperflogger/NativeModulePerfLogger.h
+++ b/packages/react-native/ReactCommon/reactperflogger/reactperflogger/NativeModulePerfLogger.h
@@ -8,8 +8,7 @@
 #pragma once
 #include <cstdint>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /**
  * A platform-agnostic interface to do performance logging on NativeModules and
@@ -160,5 +159,4 @@ class NativeModulePerfLogger {
       int32_t id) = 0;
 };
 
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react
diff --git a/packages/react-native/ReactCommon/runtimeexecutor/ReactCommon/RuntimeExecutor.h b/packages/react-native/ReactCommon/runtimeexecutor/ReactCommon/RuntimeExecutor.h
index 1c5180918d6431..94f2b5d55f3293 100644
--- a/packages/react-native/ReactCommon/runtimeexecutor/ReactCommon/RuntimeExecutor.h
+++ b/packages/react-native/ReactCommon/runtimeexecutor/ReactCommon/RuntimeExecutor.h
@@ -12,8 +12,7 @@
 
 #include <jsi/jsi.h>
 
-namespace facebook {
-namespace react {
+namespace facebook::react {
 
 /*
  * Takes a function and calls it with a reference to a Runtime. The function
@@ -125,5 +124,4 @@ inline static DataT executeSynchronouslyOnSameThread_CAN_DEADLOCK(
 
   return data;
 }
-} // namespace react
-} // namespace facebook
+} // namespace facebook::react