diff --git a/cmake/GoogleCloudCppCommon.cmake b/cmake/GoogleCloudCppCommon.cmake
index d6084628cbf52..334f2fc196eb3 100644
--- a/cmake/GoogleCloudCppCommon.cmake
+++ b/cmake/GoogleCloudCppCommon.cmake
@@ -80,6 +80,8 @@ elseif (GOOGLE_CLOUD_CPP_GENERATE_DOXYGEN)
         "GOOGLE_CLOUD_CPP_IAM_DEPRECATED(x)="
         "GOOGLE_CLOUD_CPP_BIGTABLE_IAM_DEPRECATED(x)="
         "GOOGLE_CLOUD_CPP_SPANNER_ADMIN_API_DEPRECATED(x)="
+        "GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_BEGIN=inline namespace omit_this_inline_ns {"
+        "GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END=}"
         "GOOGLE_CLOUD_CPP_NS=omit_this_inline_ns")
     set(DOXYGEN_HTML_TIMESTAMP YES)
     set(DOXYGEN_STRIP_FROM_INC_PATH "${PROJECT_SOURCE_DIR}")
diff --git a/google/cloud/version.h b/google/cloud/version.h
index 782f2d39d193d..cfd155c3b4d00 100644
--- a/google/cloud/version.h
+++ b/google/cloud/version.h
@@ -33,6 +33,24 @@
   GOOGLE_CLOUD_CPP_VEVAL(GOOGLE_CLOUD_CPP_VERSION_MAJOR, \
                          GOOGLE_CLOUD_CPP_VERSION_MINOR)
 
+/**
+ * Versioned inline namespace that users should generally avoid spelling.
+ *
+ * The actual inline namespace name will change with each release, and if you
+ * use it your code will be tightly coupled to a specific release. Omitting the
+ * inline namespace name will make upgrading to newer releases easier.
+ *
+ * However, applications may need to link multiple versions of the Google Cloud
+ * C++ Libraries, for example, if they link a library that uses an older
+ * version of the libraries than they do. This namespace is inlined, so
+ * applications can use `google::cloud::Foo` in their source, but the symbols
+ * are versioned, i.e., the symbol becomes `google::cloud::vXYZ::Foo`.
+ */
+#define GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_BEGIN \
+  inline namespace GOOGLE_CLOUD_CPP_NS {
+#define GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_END \
+  }  // namespace GOOGLE_CLOUD_CPP_NS
+
 // This preprocessor symbol is deprecated and should never be used anywhere. It
 // exists solely for backward compatibility to avoid breaking anyone who may
 // have been using it.