diff --git a/fixtures/ssr/src/components/Chrome.js b/fixtures/ssr/src/components/Chrome.js
index 5bad11aae5a27..9537f037e76eb 100644
--- a/fixtures/ssr/src/components/Chrome.js
+++ b/fixtures/ssr/src/components/Chrome.js
@@ -28,12 +28,9 @@ export default class Chrome extends Component {
             <div>
               <ThemeToggleButton
                 onChange={theme => {
-                  React.unstable_withSuspenseConfig(
-                    () => {
-                      this.setState({theme});
-                    },
-                    {timeoutMs: 6000}
-                  );
+                  React.startTransition(() => {
+                    this.setState({theme});
+                  });
                 }}
               />
             </div>
diff --git a/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js b/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
index 1d70475041491..1e6a912651832 100644
--- a/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
+++ b/packages/react-dom/src/__tests__/ReactDOMServerPartialHydration-test.internal.js
@@ -913,9 +913,8 @@ describe('ReactDOMServerPartialHydration', () => {
     expect(container.textContent).toBe('Hello');
 
     // Render an update with a long timeout.
-    React.unstable_withSuspenseConfig(
-      () => root.render(<App text="Hi" className="hi" />),
-      {timeoutMs: 5000},
+    React.unstable_startTransition(() =>
+      root.render(<App text="Hi" className="hi" />),
     );
 
     // This shouldn't force the fallback yet.
diff --git a/packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js b/packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js
index d2de57b588342..7b48d0118bebd 100644
--- a/packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js
+++ b/packages/react-dom/src/__tests__/ReactTestUtilsAct-test.js
@@ -771,14 +771,11 @@ function runActTests(label, render, unmount, rerender) {
           expect(document.querySelector('[data-test-id=spinner]')).toBeNull();
 
           // trigger a suspendy update with a delay
-          React.unstable_withSuspenseConfig(
-            () => {
-              act(() => {
-                rerender(<App suspend={true} />);
-              });
-            },
-            {timeout: 5000},
-          );
+          React.unstable_startTransition(() => {
+            act(() => {
+              rerender(<App suspend={true} />);
+            });
+          });
 
           if (label === 'concurrent mode') {
             // In Concurrent Mode, refresh transitions delay indefinitely.
diff --git a/packages/react-dom/src/events/plugins/__tests__/SimpleEventPlugin-test.js b/packages/react-dom/src/events/plugins/__tests__/SimpleEventPlugin-test.js
index 4614052f50b76..f407bef53fe89 100644
--- a/packages/react-dom/src/events/plugins/__tests__/SimpleEventPlugin-test.js
+++ b/packages/react-dom/src/events/plugins/__tests__/SimpleEventPlugin-test.js
@@ -389,14 +389,11 @@ describe('SimpleEventPlugin', function() {
             <button
               ref={el => (button = el)}
               onClick={() => {
-                React.unstable_withSuspenseConfig(
-                  () => {
-                    this.setState(state => ({
-                      lowPriCount: state.lowPriCount + 1,
-                    }));
-                  },
-                  {timeoutMs: 5000},
-                );
+                React.unstable_startTransition(() => {
+                  this.setState(state => ({
+                    lowPriCount: state.lowPriCount + 1,
+                  }));
+                });
               }}>
               {text}
             </button>
diff --git a/packages/react-reconciler/src/__tests__/ReactSuspense-test.internal.js b/packages/react-reconciler/src/__tests__/ReactSuspense-test.internal.js
index 8c709cb593971..e806070e9cca1 100644
--- a/packages/react-reconciler/src/__tests__/ReactSuspense-test.internal.js
+++ b/packages/react-reconciler/src/__tests__/ReactSuspense-test.internal.js
@@ -363,12 +363,9 @@ describe('ReactSuspense', () => {
 
       // Schedule another update. This will have lower priority because it's
       // a transition.
-      React.unstable_withSuspenseConfig(
-        () => {
-          root.update(<App shouldSuspend={false} step={2} />);
-        },
-        {timeoutMs: 10000},
-      );
+      React.unstable_startTransition(() => {
+        root.update(<App shouldSuspend={false} step={2} />);
+      });
 
       // Interrupt to trigger a restart.
       interrupt();
@@ -465,12 +462,9 @@ describe('ReactSuspense', () => {
 
         // Schedule another update. This will have lower priority because it's
         // a transition.
-        React.unstable_withSuspenseConfig(
-          () => {
-            setShouldHideInParent(true);
-          },
-          {timeoutMs: 10000},
-        );
+        React.unstable_startTransition(() => {
+          setShouldHideInParent(true);
+        });
 
         expect(Scheduler).toFlushAndYieldThrough([
           // Should have restarted the first update, because of the interruption
diff --git a/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js b/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
index 035bd8bc57537..9ca9f545eb82b 100644
--- a/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactSuspenseWithNoopRenderer-test.js
@@ -959,12 +959,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     expect(Scheduler).toFlushAndYield(['S']);
 
     // Schedule an update, and suspend for up to 5 seconds.
-    React.unstable_withSuspenseConfig(
-      () => ReactNoop.render(<App text="A" />),
-      {
-        timeoutMs: 5000,
-      },
-    );
+    React.unstable_startTransition(() => ReactNoop.render(<App text="A" />));
     // The update should suspend.
     expect(Scheduler).toFlushAndYield(['Suspend! [A]', 'Loading...']);
     expect(ReactNoop.getChildren()).toEqual([span('S')]);
@@ -976,12 +971,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     expect(ReactNoop.getChildren()).toEqual([span('S')]);
 
     // Schedule another low priority update.
-    React.unstable_withSuspenseConfig(
-      () => ReactNoop.render(<App text="B" />),
-      {
-        timeoutMs: 10000,
-      },
-    );
+    React.unstable_startTransition(() => ReactNoop.render(<App text="B" />));
     // This update should also suspend.
     expect(Scheduler).toFlushAndYield(['Suspend! [B]', 'Loading...']);
     expect(ReactNoop.getChildren()).toEqual([span('S')]);
@@ -2282,7 +2272,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     ReactNoop.render(<Foo renderContent={1} />);
 
     // Took a long time to render. This is to ensure we get a long suspense time.
-    // Could also use something like withSuspenseConfig to simulate this.
+    // Could also use something like startTransition to simulate this.
     Scheduler.unstable_advanceTime(1500);
     await advanceTimers(1500);
 
@@ -2330,10 +2320,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
       }
 
       // Initial render.
-      React.unstable_withSuspenseConfig(
-        () => ReactNoop.render(<App page="A" />),
-        SUSPENSE_CONFIG,
-      );
+      React.unstable_startTransition(() => ReactNoop.render(<App page="A" />));
 
       expect(Scheduler).toFlushAndYield(['Suspend! [A]', 'Loading...']);
       // Only a short time is needed to unsuspend the initial loading state.
@@ -2349,10 +2336,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
       expect(ReactNoop.getChildren()).toEqual([span('A')]);
 
       // Start transition.
-      React.unstable_withSuspenseConfig(
-        () => ReactNoop.render(<App page="B" />),
-        SUSPENSE_CONFIG,
-      );
+      React.unstable_startTransition(() => ReactNoop.render(<App page="B" />));
 
       expect(Scheduler).toFlushAndYield(['Suspend! [B]', 'Loading...']);
       Scheduler.unstable_advanceTime(100000);
@@ -2389,10 +2373,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
       // Initial render.
       await ReactNoop.act(async () => {
-        React.unstable_withSuspenseConfig(
-          () => transitionToPage('A'),
-          SUSPENSE_CONFIG,
-        );
+        React.unstable_startTransition(() => transitionToPage('A'));
 
         expect(Scheduler).toFlushAndYield(['Suspend! [A]', 'Loading...']);
         // Only a short time is needed to unsuspend the initial loading state.
@@ -2409,10 +2390,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
       // Start transition.
       await ReactNoop.act(async () => {
-        React.unstable_withSuspenseConfig(
-          () => transitionToPage('B'),
-          SUSPENSE_CONFIG,
-        );
+        React.unstable_startTransition(() => transitionToPage('B'));
 
         expect(Scheduler).toFlushAndYield(['Suspend! [B]', 'Loading...']);
         Scheduler.unstable_advanceTime(100000);
@@ -2452,10 +2430,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
       // Initial render.
       await ReactNoop.act(async () => {
-        React.unstable_withSuspenseConfig(
-          () => transitionToPage('A'),
-          SUSPENSE_CONFIG,
-        );
+        React.unstable_startTransition(() => transitionToPage('A'));
 
         expect(Scheduler).toFlushAndYield(['Suspend! [A]', 'Loading...']);
         // Only a short time is needed to unsuspend the initial loading state.
@@ -2472,10 +2447,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
 
       // Start transition.
       await ReactNoop.act(async () => {
-        React.unstable_withSuspenseConfig(
-          () => transitionToPage('B'),
-          SUSPENSE_CONFIG,
-        );
+        React.unstable_startTransition(() => transitionToPage('B'));
 
         expect(Scheduler).toFlushAndYield(['Suspend! [B]', 'Loading...']);
         Scheduler.unstable_advanceTime(100000);
@@ -2689,75 +2661,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
   });
 
   // @gate experimental
-  it('disables suspense config when nothing is passed to withSuspenseConfig', async () => {
-    function App({page}) {
-      return (
-        <Suspense fallback={<Text text="Loading..." />}>
-          <AsyncText text={page} ms={2000} />
-        </Suspense>
-      );
-    }
-
-    // Initial render.
-    ReactNoop.render(<App page="A" />);
-    expect(Scheduler).toFlushAndYield(['Suspend! [A]', 'Loading...']);
-    Scheduler.unstable_advanceTime(2000);
-    await advanceTimers(2000);
-    expect(Scheduler).toHaveYielded(['Promise resolved [A]']);
-    expect(Scheduler).toFlushAndYield(['A']);
-    expect(ReactNoop.getChildren()).toEqual([span('A')]);
-
-    // Start transition.
-    React.unstable_withSuspenseConfig(
-      () => {
-        // When we schedule an inner transition without a suspense config
-        // so it should only suspend for a short time.
-        React.unstable_withSuspenseConfig(() =>
-          ReactNoop.render(<App page="B" />),
-        );
-      },
-      {timeoutMs: 2000},
-    );
-
-    expect(Scheduler).toFlushAndYield(['Suspend! [B]', 'Loading...']);
-    // Suspended
-    expect(ReactNoop.getChildren()).toEqual([span('A')]);
-    Scheduler.unstable_advanceTime(500);
-    await advanceTimers(500);
-    // Committed loading state.
-    expect(ReactNoop.getChildren()).toEqual([
-      hiddenSpan('A'),
-      span('Loading...'),
-    ]);
-
-    Scheduler.unstable_advanceTime(2000);
-    await advanceTimers(2000);
-    expect(Scheduler).toHaveYielded(['Promise resolved [B]']);
-    expect(Scheduler).toFlushAndYield(['B']);
-    expect(ReactNoop.getChildren()).toEqual([span('B')]);
-
-    React.unstable_withSuspenseConfig(
-      () => {
-        // First we schedule an inner unrelated update.
-        React.unstable_withSuspenseConfig(() =>
-          ReactNoop.render(<App page="B" unrelated={true} />),
-        );
-        // Then we schedule another transition to a slow page,
-        // but at this scope we should suspend for longer.
-        Scheduler.unstable_next(() => ReactNoop.render(<App page="C" />));
-      },
-      {timeoutMs: 60000},
-    );
-    expect(Scheduler).toFlushAndYield(['B', 'Suspend! [C]', 'Loading...']);
-    expect(ReactNoop.getChildren()).toEqual([span('B')]);
-    // Event after a large amount of time, we never show a loading state.
-    Scheduler.unstable_advanceTime(60000);
-    await advanceTimers(60000);
-    expect(ReactNoop.getChildren()).toEqual([span('B')]);
-  });
-
-  // @gate experimental
-  it('withSuspenseConfig delay applies when we use an updated avoided boundary', async () => {
+  it('do not show placeholder when updating an avoided boundary with startTransition', async () => {
     function App({page}) {
       return (
         <Suspense fallback={<Text text="Loading..." />}>
@@ -2780,10 +2684,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     expect(ReactNoop.getChildren()).toEqual([span('Hi!'), span('A')]);
 
     // Start transition.
-    React.unstable_withSuspenseConfig(
-      () => ReactNoop.render(<App page="B" />),
-      {timeoutMs: 2000},
-    );
+    React.unstable_startTransition(() => ReactNoop.render(<App page="B" />));
 
     expect(Scheduler).toFlushAndYield(['Hi!', 'Suspend! [B]', 'Loading B...']);
 
@@ -2806,7 +2707,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
   });
 
   // @gate experimental
-  it('withSuspenseConfig delay applies when we use a newly created avoided boundary', async () => {
+  it('do not show placeholder when mounting an avoided boundary with startTransition', async () => {
     function App({page}) {
       return (
         <Suspense fallback={<Text text="Loading..." />}>
@@ -2830,10 +2731,7 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     expect(ReactNoop.getChildren()).toEqual([span('Hi!'), span('A')]);
 
     // Start transition.
-    React.unstable_withSuspenseConfig(
-      () => ReactNoop.render(<App page="B" />),
-      {timeoutMs: 2000},
-    );
+    React.unstable_startTransition(() => ReactNoop.render(<App page="B" />));
 
     expect(Scheduler).toFlushAndYield(['Hi!', 'Suspend! [B]', 'Loading B...']);
 
@@ -2992,12 +2890,9 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     expect(ReactNoop).toMatchRenderedOutput(<div hidden={true} />);
 
     // Start transition.
-    React.unstable_withSuspenseConfig(
-      () => {
-        ReactNoop.render(<App showContent={true} />);
-      },
-      {timeoutMs: 2500},
-    );
+    React.unstable_startTransition(() => {
+      ReactNoop.render(<App showContent={true} />);
+    });
 
     expect(Scheduler).toFlushAndYield(['Suspend! [A]', 'Loading...']);
     Scheduler.unstable_advanceTime(2000);
@@ -3049,12 +2944,9 @@ describe('ReactSuspenseWithNoopRenderer', () => {
     expect(Scheduler).toFlushAndYieldThrough(['Suspend! [A]']);
 
     // Start transition.
-    React.unstable_withSuspenseConfig(
-      () => {
-        ReactNoop.render(<App showContent={true} />);
-      },
-      {timeoutMs: 5000},
-    );
+    React.unstable_startTransition(() => {
+      ReactNoop.render(<App showContent={true} />);
+    });
 
     expect(Scheduler).toFlushAndYield(['Suspend! [A]', 'Loading...']);
     Scheduler.unstable_advanceTime(2000);
diff --git a/packages/react/index.classic.fb.js b/packages/react/index.classic.fb.js
index 50285328818b7..5f79d3de1fef3 100644
--- a/packages/react/index.classic.fb.js
+++ b/packages/react/index.classic.fb.js
@@ -50,7 +50,6 @@ export {
   startTransition as unstable_startTransition,
   SuspenseList,
   SuspenseList as unstable_SuspenseList,
-  unstable_withSuspenseConfig,
   // enableBlocksAPI
   block,
   block as unstable_block,
diff --git a/packages/react/index.experimental.js b/packages/react/index.experimental.js
index ff00b13333da8..0b5e7efd13505 100644
--- a/packages/react/index.experimental.js
+++ b/packages/react/index.experimental.js
@@ -44,7 +44,6 @@ export {
   useDeferredValue as unstable_useDeferredValue,
   startTransition as unstable_startTransition,
   SuspenseList as unstable_SuspenseList,
-  unstable_withSuspenseConfig,
   // enableBlocksAPI
   block as unstable_block,
   unstable_useOpaqueIdentifier,
diff --git a/packages/react/index.js b/packages/react/index.js
index ebbb6cf42e6ba..9fd5ccfbf37fb 100644
--- a/packages/react/index.js
+++ b/packages/react/index.js
@@ -78,7 +78,6 @@ export {
   useDeferredValue as unstable_useDeferredValue,
   SuspenseList,
   SuspenseList as unstable_SuspenseList,
-  unstable_withSuspenseConfig,
   block,
   block as unstable_block,
   unstable_LegacyHidden,
diff --git a/packages/react/index.modern.fb.js b/packages/react/index.modern.fb.js
index fb2e1dcbef4f2..a5b509460d896 100644
--- a/packages/react/index.modern.fb.js
+++ b/packages/react/index.modern.fb.js
@@ -49,7 +49,6 @@ export {
   startTransition as unstable_startTransition,
   SuspenseList,
   SuspenseList as unstable_SuspenseList,
-  unstable_withSuspenseConfig,
   // enableBlocksAPI
   block,
   block as unstable_block,
diff --git a/packages/react/src/React.js b/packages/react/src/React.js
index bd737472a5eb8..d5367da328bb5 100644
--- a/packages/react/src/React.js
+++ b/packages/react/src/React.js
@@ -49,7 +49,6 @@ import {
   useDeferredValue,
   useOpaqueIdentifier,
 } from './ReactHooks';
-import {withSuspenseConfig} from './ReactBatchConfig';
 import {
   createElementWithValidation,
   createFactoryWithValidation,
@@ -112,7 +111,6 @@ export {
   useDeferredValue,
   REACT_SUSPENSE_LIST_TYPE as SuspenseList,
   REACT_LEGACY_HIDDEN_TYPE as unstable_LegacyHidden,
-  withSuspenseConfig as unstable_withSuspenseConfig,
   // enableBlocksAPI
   block,
   // enableFundamentalAPI
diff --git a/packages/react/src/ReactBatchConfig.js b/packages/react/src/ReactBatchConfig.js
deleted file mode 100644
index c08dac615486c..0000000000000
--- a/packages/react/src/ReactBatchConfig.js
+++ /dev/null
@@ -1,25 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @flow
- */
-
-import ReactCurrentBatchConfig from './ReactCurrentBatchConfig';
-
-// This is a copy of startTransition, except if null or undefined is passed,
-// then updates inside the scope are opted-out of the outer transition scope.
-// TODO: Deprecated. Remove in favor of startTransition. Figure out how scopes
-// should nest, and whether we need an API to opt-out nested scopes.
-export function withSuspenseConfig(scope: () => void, config?: mixed) {
-  const prevTransition = ReactCurrentBatchConfig.transition;
-  ReactCurrentBatchConfig.transition =
-    config === undefined || config === null ? 0 : 1;
-  try {
-    scope();
-  } finally {
-    ReactCurrentBatchConfig.transition = prevTransition;
-  }
-}