diff --git a/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js b/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
index 2b93c8f06e2b2..e245adcb1380a 100644
--- a/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
+++ b/packages/react-debug-tools/src/__tests__/ReactHooksInspectionIntegration-test.js
@@ -14,7 +14,6 @@ let React;
 let ReactTestRenderer;
 let ReactDebugTools;
 let act;
-let assertConsoleErrorDev;
 let useMemoCache;
 
 function normalizeSourceLoc(tree) {
@@ -34,7 +33,7 @@ describe('ReactHooksInspectionIntegration', () => {
     jest.resetModules();
     React = require('react');
     ReactTestRenderer = require('react-test-renderer');
-    ({act, assertConsoleErrorDev} = require('internal-test-utils'));
+    ({act} = require('internal-test-utils'));
     ReactDebugTools = require('react-debug-tools');
     useMemoCache = require('react/compiler-runtime').c;
   });
@@ -2321,57 +2320,6 @@ describe('ReactHooksInspectionIntegration', () => {
     });
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('should support defaultProps and lazy', async () => {
-    const Suspense = React.Suspense;
-
-    function Foo(props) {
-      const [value] = React.useState(props.defaultValue.slice(0, 3));
-      return <div>{value}</div>;
-    }
-    Foo.defaultProps = {
-      defaultValue: 'default',
-    };
-
-    async function fakeImport(result) {
-      return {default: result};
-    }
-
-    const LazyFoo = React.lazy(() => fakeImport(Foo));
-
-    const renderer = ReactTestRenderer.create(
-      <Suspense fallback="Loading...">
-        <LazyFoo />
-      </Suspense>,
-    );
-
-    await act(async () => await LazyFoo);
-    assertConsoleErrorDev([
-      'Foo: Support for defaultProps will be removed from function components in a future major release. Use JavaScript default parameters instead.',
-    ]);
-
-    const childFiber = renderer.root._currentFiber();
-    const tree = ReactDebugTools.inspectHooksOfFiber(childFiber);
-    expect(normalizeSourceLoc(tree)).toMatchInlineSnapshot(`
-      [
-        {
-          "debugInfo": null,
-          "hookSource": {
-            "columnNumber": 0,
-            "fileName": "**",
-            "functionName": "Foo",
-            "lineNumber": 0,
-          },
-          "id": 0,
-          "isStateEditable": true,
-          "name": "State",
-          "subHooks": [],
-          "value": "def",
-        },
-      ]
-    `);
-  });
-
   // This test case is based on an open source bug report:
   // https://github.com/facebookincubator/redux-react-hook/issues/34#issuecomment-466693787
   it('should properly advance the current hook for useContext', async () => {
diff --git a/packages/react-dom/src/__tests__/ReactDeprecationWarnings-test.js b/packages/react-dom/src/__tests__/ReactDeprecationWarnings-test.js
deleted file mode 100644
index 523f1167ab612..0000000000000
--- a/packages/react-dom/src/__tests__/ReactDeprecationWarnings-test.js
+++ /dev/null
@@ -1,72 +0,0 @@
-/**
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- *
- * @emails react-core
- */
-
-'use strict';
-
-let React;
-let ReactNoop;
-let waitForAll;
-let assertConsoleErrorDev;
-
-describe('ReactDeprecationWarnings', () => {
-  beforeEach(() => {
-    jest.resetModules();
-    React = require('react');
-    ReactNoop = require('react-noop-renderer');
-    const InternalTestUtils = require('internal-test-utils');
-    waitForAll = InternalTestUtils.waitForAll;
-    assertConsoleErrorDev = InternalTestUtils.assertConsoleErrorDev;
-  });
-
-  // @gate !disableDefaultPropsExceptForClasses || !__DEV__
-  it('should warn when given defaultProps', async () => {
-    function FunctionalComponent(props) {
-      return null;
-    }
-
-    FunctionalComponent.defaultProps = {
-      testProp: true,
-    };
-
-    ReactNoop.render(<FunctionalComponent />);
-    await waitForAll([]);
-    assertConsoleErrorDev([
-      'FunctionalComponent: Support for defaultProps ' +
-        'will be removed from function components in a future major ' +
-        'release. Use JavaScript default parameters instead.\n' +
-        '    in FunctionalComponent (at **)',
-    ]);
-  });
-
-  // @gate !disableDefaultPropsExceptForClasses || !__DEV__
-  it('should warn when given defaultProps on a memoized function', async () => {
-    const MemoComponent = React.memo(function FunctionalComponent(props) {
-      return null;
-    });
-
-    MemoComponent.defaultProps = {
-      testProp: true,
-    };
-
-    ReactNoop.render(
-      <div>
-        <MemoComponent />
-      </div>,
-    );
-    await waitForAll([]);
-    assertConsoleErrorDev(
-      [
-        'FunctionalComponent: Support for defaultProps ' +
-          'will be removed from memo components in a future major ' +
-          'release. Use JavaScript default parameters instead.',
-      ],
-      {withoutStack: true},
-    );
-  });
-});
diff --git a/packages/react-dom/src/__tests__/ReactFunctionComponent-test.js b/packages/react-dom/src/__tests__/ReactFunctionComponent-test.js
index dc117f544cdf7..80f9779fdd17b 100644
--- a/packages/react-dom/src/__tests__/ReactFunctionComponent-test.js
+++ b/packages/react-dom/src/__tests__/ReactFunctionComponent-test.js
@@ -205,27 +205,6 @@ describe('ReactFunctionComponent', () => {
     ]);
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('should support default props', async () => {
-    function Child(props) {
-      return <div>{props.test}</div>;
-    }
-    Child.defaultProps = {test: 2};
-
-    const container = document.createElement('div');
-    const root = ReactDOMClient.createRoot(container);
-
-    await act(() => {
-      root.render(<Child />);
-    });
-    expect(container.textContent).toBe('2');
-    assertConsoleErrorDev([
-      'Child: Support for defaultProps will be removed from function components in a future major release. ' +
-        'Use JavaScript default parameters instead.\n' +
-        '    in Child (at **)',
-    ]);
-  });
-
   // @gate !disableLegacyContext && !disableLegacyContextForFunctionComponents
   it('should receive context', async () => {
     class Parent extends React.Component {
diff --git a/packages/react-reconciler/src/ReactFiberBeginWork.js b/packages/react-reconciler/src/ReactFiberBeginWork.js
index c195e840e6eb1..1b0b6b8d97310 100644
--- a/packages/react-reconciler/src/ReactFiberBeginWork.js
+++ b/packages/react-reconciler/src/ReactFiberBeginWork.js
@@ -117,7 +117,6 @@ import {
   enableCPUSuspense,
   enablePostpone,
   disableLegacyMode,
-  disableDefaultPropsExceptForClasses,
   enableHydrationLaneScheduling,
   enableViewTransition,
   enableFragmentRefs,
@@ -258,7 +257,6 @@ import {
   updateClassInstance,
   resolveClassComponentProps,
 } from './ReactFiberClassComponent';
-import {resolveDefaultPropsOnNonClassComponent} from './ReactFiberLazyComponent';
 import {
   createFiberFromTypeAndProps,
   createFiberFromFragment,
@@ -327,7 +325,6 @@ let didWarnAboutGetDerivedStateOnFunctionComponent;
 export let didWarnAboutReassigningProps: boolean;
 let didWarnAboutRevealOrder;
 let didWarnAboutTailOptions;
-let didWarnAboutDefaultPropsOnFunctionComponent;
 let didWarnAboutClassNameOnViewTransition;
 
 if (__DEV__) {
@@ -338,7 +335,6 @@ if (__DEV__) {
   didWarnAboutReassigningProps = false;
   didWarnAboutRevealOrder = ({}: {[string]: boolean});
   didWarnAboutTailOptions = ({}: {[string]: boolean});
-  didWarnAboutDefaultPropsOnFunctionComponent = ({}: {[string]: boolean});
   didWarnAboutClassNameOnViewTransition = ({}: {[string]: boolean});
 }
 
@@ -482,13 +478,7 @@ function updateMemoComponent(
 ): null | Fiber {
   if (current === null) {
     const type = Component.type;
-    if (
-      isSimpleFunctionComponent(type) &&
-      Component.compare === null &&
-      // SimpleMemoComponent codepath doesn't resolve outer props either.
-      (disableDefaultPropsExceptForClasses ||
-        Component.defaultProps === undefined)
-    ) {
+    if (isSimpleFunctionComponent(type) && Component.compare === null) {
       let resolvedType = type;
       if (__DEV__) {
         resolvedType = resolveFunctionForHotReloading(type);
@@ -509,21 +499,6 @@ function updateMemoComponent(
         renderLanes,
       );
     }
-    if (!disableDefaultPropsExceptForClasses) {
-      if (__DEV__) {
-        if (Component.defaultProps !== undefined) {
-          const componentName = getComponentNameFromType(type) || 'Unknown';
-          if (!didWarnAboutDefaultPropsOnFunctionComponent[componentName]) {
-            console.error(
-              '%s: Support for defaultProps will be removed from memo components ' +
-                'in a future major release. Use JavaScript default parameters instead.',
-              componentName,
-            );
-            didWarnAboutDefaultPropsOnFunctionComponent[componentName] = true;
-          }
-        }
-      }
-    }
     const child = createFiberFromTypeAndProps(
       Component.type,
       null,
@@ -2072,9 +2047,6 @@ function mountLazyComponent(
         renderLanes,
       );
     } else {
-      const resolvedProps = disableDefaultPropsExceptForClasses
-        ? props
-        : resolveDefaultPropsOnNonClassComponent(Component, props);
       workInProgress.tag = FunctionComponent;
       if (__DEV__) {
         validateFunctionComponentInDev(workInProgress, Component);
@@ -2085,16 +2057,13 @@ function mountLazyComponent(
         null,
         workInProgress,
         Component,
-        resolvedProps,
+        props,
         renderLanes,
       );
     }
   } else if (Component !== undefined && Component !== null) {
     const $$typeof = Component.$$typeof;
     if ($$typeof === REACT_FORWARD_REF_TYPE) {
-      const resolvedProps = disableDefaultPropsExceptForClasses
-        ? props
-        : resolveDefaultPropsOnNonClassComponent(Component, props);
       workInProgress.tag = ForwardRef;
       if (__DEV__) {
         workInProgress.type = Component =
@@ -2104,24 +2073,16 @@ function mountLazyComponent(
         null,
         workInProgress,
         Component,
-        resolvedProps,
+        props,
         renderLanes,
       );
     } else if ($$typeof === REACT_MEMO_TYPE) {
-      const resolvedProps = disableDefaultPropsExceptForClasses
-        ? props
-        : resolveDefaultPropsOnNonClassComponent(Component, props);
       workInProgress.tag = MemoComponent;
       return updateMemoComponent(
         null,
         workInProgress,
         Component,
-        disableDefaultPropsExceptForClasses
-          ? resolvedProps
-          : resolveDefaultPropsOnNonClassComponent(
-              Component.type,
-              resolvedProps,
-            ), // The inner type can have defaults too
+        props,
         renderLanes,
       );
     }
@@ -2198,22 +2159,6 @@ function validateFunctionComponentInDev(workInProgress: Fiber, Component: any) {
       );
     }
 
-    if (
-      !disableDefaultPropsExceptForClasses &&
-      Component.defaultProps !== undefined
-    ) {
-      const componentName = getComponentNameFromType(Component) || 'Unknown';
-
-      if (!didWarnAboutDefaultPropsOnFunctionComponent[componentName]) {
-        console.error(
-          '%s: Support for defaultProps will be removed from function components ' +
-            'in a future major release. Use JavaScript default parameters instead.',
-          componentName,
-        );
-        didWarnAboutDefaultPropsOnFunctionComponent[componentName] = true;
-      }
-    }
-
     if (typeof Component.getDerivedStateFromProps === 'function') {
       const componentName = getComponentNameFromType(Component) || 'Unknown';
 
@@ -4175,17 +4120,11 @@ function beginWork(
     }
     case FunctionComponent: {
       const Component = workInProgress.type;
-      const unresolvedProps = workInProgress.pendingProps;
-      const resolvedProps =
-        disableDefaultPropsExceptForClasses ||
-        workInProgress.elementType === Component
-          ? unresolvedProps
-          : resolveDefaultPropsOnNonClassComponent(Component, unresolvedProps);
       return updateFunctionComponent(
         current,
         workInProgress,
         Component,
-        resolvedProps,
+        workInProgress.pendingProps,
         renderLanes,
       );
     }
@@ -4226,18 +4165,11 @@ function beginWork(
     case HostPortal:
       return updatePortalComponent(current, workInProgress, renderLanes);
     case ForwardRef: {
-      const type = workInProgress.type;
-      const unresolvedProps = workInProgress.pendingProps;
-      const resolvedProps =
-        disableDefaultPropsExceptForClasses ||
-        workInProgress.elementType === type
-          ? unresolvedProps
-          : resolveDefaultPropsOnNonClassComponent(type, unresolvedProps);
       return updateForwardRef(
         current,
         workInProgress,
-        type,
-        resolvedProps,
+        workInProgress.type,
+        workInProgress.pendingProps,
         renderLanes,
       );
     }
@@ -4252,20 +4184,11 @@ function beginWork(
     case ContextConsumer:
       return updateContextConsumer(current, workInProgress, renderLanes);
     case MemoComponent: {
-      const type = workInProgress.type;
-      const unresolvedProps = workInProgress.pendingProps;
-      // Resolve outer props first, then resolve inner props.
-      let resolvedProps = disableDefaultPropsExceptForClasses
-        ? unresolvedProps
-        : resolveDefaultPropsOnNonClassComponent(type, unresolvedProps);
-      resolvedProps = disableDefaultPropsExceptForClasses
-        ? resolvedProps
-        : resolveDefaultPropsOnNonClassComponent(type.type, resolvedProps);
       return updateMemoComponent(
         current,
         workInProgress,
-        type,
-        resolvedProps,
+        workInProgress.type,
+        workInProgress.pendingProps,
         renderLanes,
       );
     }
diff --git a/packages/react-reconciler/src/ReactFiberClassComponent.js b/packages/react-reconciler/src/ReactFiberClassComponent.js
index 7076c678833dc..7a9b443b3c282 100644
--- a/packages/react-reconciler/src/ReactFiberClassComponent.js
+++ b/packages/react-reconciler/src/ReactFiberClassComponent.js
@@ -20,7 +20,6 @@ import {
 import {
   disableLegacyContext,
   enableSchedulingProfiler,
-  disableDefaultPropsExceptForClasses,
 } from 'shared/ReactFeatureFlags';
 import ReactStrictModeWarnings from './ReactStrictModeWarnings';
 import {get as getInstance, set as setInstance} from 'shared/ReactInstanceMap';
@@ -1214,12 +1213,7 @@ export function resolveClassComponentProps(
 
   // Resolve default props.
   const defaultProps = Component.defaultProps;
-  if (
-    defaultProps &&
-    // If disableDefaultPropsExceptForClasses is true, we always resolve
-    // default props here in the reconciler, rather than in the JSX runtime.
-    (disableDefaultPropsExceptForClasses || !alreadyResolvedDefaultProps)
-  ) {
+  if (defaultProps) {
     // We may have already copied the props object above to remove ref. If so,
     // we can modify that. Otherwise, copy the props object with Object.assign.
     if (newProps === baseProps) {
diff --git a/packages/react-reconciler/src/ReactFiberLazyComponent.js b/packages/react-reconciler/src/ReactFiberLazyComponent.js
deleted file mode 100644
index 36e16c2b40800..0000000000000
--- a/packages/react-reconciler/src/ReactFiberLazyComponent.js
+++ /dev/null
@@ -1,34 +0,0 @@
-/**
- * Copyright (c) Meta Platforms, Inc. and 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 assign from 'shared/assign';
-import {disableDefaultPropsExceptForClasses} from 'shared/ReactFeatureFlags';
-
-export function resolveDefaultPropsOnNonClassComponent(
-  Component: any,
-  baseProps: Object,
-): Object {
-  if (disableDefaultPropsExceptForClasses) {
-    // Support for defaultProps is removed in React 19 for all types
-    // except classes.
-    return baseProps;
-  }
-  if (Component && Component.defaultProps) {
-    // Resolve default props. Taken from ReactElement
-    const props = assign({}, baseProps);
-    const defaultProps = Component.defaultProps;
-    for (const propName in defaultProps) {
-      if (props[propName] === undefined) {
-        props[propName] = defaultProps[propName];
-      }
-    }
-    return props;
-  }
-  return baseProps;
-}
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.js b/packages/react-reconciler/src/ReactFiberWorkLoop.js
index a8b5dfadeb736..1107c5bd4624d 100644
--- a/packages/react-reconciler/src/ReactFiberWorkLoop.js
+++ b/packages/react-reconciler/src/ReactFiberWorkLoop.js
@@ -46,7 +46,6 @@ import {
   alwaysThrottleRetries,
   enableInfiniteRenderLoopDetection,
   disableLegacyMode,
-  disableDefaultPropsExceptForClasses,
   enableComponentPerformanceTrack,
   enableYieldingBeforePassive,
   enableThrottledScheduling,
@@ -349,7 +348,6 @@ import {
   getSuspenseHandler,
   getShellBoundary,
 } from './ReactFiberSuspenseContext';
-import {resolveDefaultPropsOnNonClassComponent} from './ReactFiberLazyComponent';
 import {resetChildReconcilerOnUnwind} from './ReactChildFiber';
 import {
   ensureRootIsScheduled,
@@ -2858,12 +2856,6 @@ function replayBeginWork(unitOfWork: Fiber): null | Fiber {
       // could maybe use this as an opportunity to say `use` doesn't work with
       // `defaultProps` :)
       const Component = unitOfWork.type;
-      const unresolvedProps = unitOfWork.pendingProps;
-      const resolvedProps =
-        disableDefaultPropsExceptForClasses ||
-        unitOfWork.elementType === Component
-          ? unresolvedProps
-          : resolveDefaultPropsOnNonClassComponent(Component, unresolvedProps);
       let context: any;
       if (!disableLegacyContext) {
         const unmaskedContext = getUnmaskedContext(unitOfWork, Component, true);
@@ -2872,7 +2864,7 @@ function replayBeginWork(unitOfWork: Fiber): null | Fiber {
       next = replayFunctionComponent(
         current,
         unitOfWork,
-        resolvedProps,
+        unitOfWork.pendingProps,
         Component,
         context,
         workInProgressRootRenderLanes,
@@ -2885,17 +2877,10 @@ function replayBeginWork(unitOfWork: Fiber): null | Fiber {
       // could maybe use this as an opportunity to say `use` doesn't work with
       // `defaultProps` :)
       const Component = unitOfWork.type.render;
-      const unresolvedProps = unitOfWork.pendingProps;
-      const resolvedProps =
-        disableDefaultPropsExceptForClasses ||
-        unitOfWork.elementType === Component
-          ? unresolvedProps
-          : resolveDefaultPropsOnNonClassComponent(Component, unresolvedProps);
-
       next = replayFunctionComponent(
         current,
         unitOfWork,
-        resolvedProps,
+        unitOfWork.pendingProps,
         Component,
         unitOfWork.ref,
         workInProgressRootRenderLanes,
diff --git a/packages/react-reconciler/src/__tests__/ReactLazy-test.internal.js b/packages/react-reconciler/src/__tests__/ReactLazy-test.internal.js
index b6ae8e2ba1281..27404eee5e2c8 100644
--- a/packages/react-reconciler/src/__tests__/ReactLazy-test.internal.js
+++ b/packages/react-reconciler/src/__tests__/ReactLazy-test.internal.js
@@ -701,64 +701,6 @@ describe('ReactLazy', () => {
     expect(root).toMatchRenderedOutput('A3');
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('resolves defaultProps on the outer wrapper but warns', async () => {
-    function T(props) {
-      Scheduler.log(props.inner + ' ' + props.outer);
-      return props.inner + ' ' + props.outer;
-    }
-    T.defaultProps = {inner: 'Hi'};
-    const LazyText = lazy(() => fakeImport(T));
-    LazyText.defaultProps = {outer: 'Bye'};
-    assertConsoleErrorDev(
-      [
-        'It is not supported to assign `defaultProps` to ' +
-          'a lazy component import. Either specify them where the component ' +
-          'is defined, or create a wrapping component around it.',
-      ],
-      {withoutStack: true},
-    );
-
-    const root = ReactTestRenderer.create(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyText />
-      </Suspense>,
-      {
-        unstable_isConcurrent: true,
-      },
-    );
-
-    await waitForAll(['Loading...']);
-    expect(root).not.toMatchRenderedOutput('Hi Bye');
-
-    await act(() => resolveFakeImport(T));
-    assertLog(['Hi Bye']);
-    assertConsoleErrorDev([
-      'T: Support for defaultProps ' +
-        'will be removed from function components in a future major ' +
-        'release. Use JavaScript default parameters instead.\n' +
-        '    in T (at **)',
-    ]);
-
-    expect(root).toMatchRenderedOutput('Hi Bye');
-
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyText outer="World" />
-      </Suspense>,
-    );
-    await waitForAll(['Hi World']);
-    expect(root).toMatchRenderedOutput('Hi World');
-
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyText inner="Friends" />
-      </Suspense>,
-    );
-    await waitForAll(['Friends Bye']);
-    expect(root).toMatchRenderedOutput('Friends Bye');
-  });
-
   it('throws with a useful error when wrapping invalid type with lazy()', async () => {
     const BadLazy = lazy(() => fakeImport(42));
 
@@ -1112,48 +1054,6 @@ describe('ReactLazy', () => {
     );
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('resolves props for function component with defaultProps', async () => {
-    function Add(props) {
-      expect(props.innerWithDefault).toBe(42);
-      return props.inner + props.outer;
-    }
-    Add.defaultProps = {
-      innerWithDefault: 42,
-    };
-    const LazyAdd = lazy(() => fakeImport(Add));
-    const root = ReactTestRenderer.create(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd inner="2" outer="2" />
-      </Suspense>,
-      {
-        unstable_isConcurrent: true,
-      },
-    );
-
-    await waitForAll(['Loading...']);
-    expect(root).not.toMatchRenderedOutput('22');
-
-    // Mount
-    await act(() => resolveFakeImport(Add));
-
-    assertConsoleErrorDev([
-      'Add: Support for defaultProps will be removed from function components in a future major release. Use JavaScript default parameters instead.\n' +
-        '    in Add (at **)',
-    ]);
-
-    expect(root).toMatchRenderedOutput('22');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd inner={false} outer={false} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('0');
-  });
-
   it('resolves props for function component without defaultProps', async () => {
     function Add(props) {
       return props.inner + props.outer;
@@ -1258,44 +1158,6 @@ describe('ReactLazy', () => {
     expect(root).toMatchRenderedOutput('0');
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('resolves props for forwardRef component with defaultProps', async () => {
-    const Add = React.forwardRef((props, ref) => {
-      expect(props.innerWithDefault).toBe(42);
-      return props.inner + props.outer;
-    });
-    Add.displayName = 'Add';
-    Add.defaultProps = {
-      innerWithDefault: 42,
-    };
-    const LazyAdd = lazy(() => fakeImport(Add));
-    const root = ReactTestRenderer.create(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd inner="2" outer="2" />
-      </Suspense>,
-      {
-        unstable_isConcurrent: true,
-      },
-    );
-
-    await waitForAll(['Loading...']);
-    expect(root).not.toMatchRenderedOutput('22');
-
-    // Mount
-    await act(() => resolveFakeImport(Add));
-
-    expect(root).toMatchRenderedOutput('22');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd inner={false} outer={false} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('0');
-  });
-
   it('resolves props for forwardRef component without defaultProps', async () => {
     const Add = React.forwardRef((props, ref) => {
       return props.inner + props.outer;
@@ -1330,51 +1192,6 @@ describe('ReactLazy', () => {
     expect(root).toMatchRenderedOutput('0');
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('resolves props for outer memo component with defaultProps', async () => {
-    let Add = props => {
-      expect(props.innerWithDefault).toBe(42);
-      return props.inner + props.outer;
-    };
-    Add = React.memo(Add);
-    Add.defaultProps = {
-      innerWithDefault: 42,
-    };
-    const LazyAdd = lazy(() => fakeImport(Add));
-    const root = ReactTestRenderer.create(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd inner="2" outer="2" />
-      </Suspense>,
-      {
-        unstable_isConcurrent: true,
-      },
-    );
-
-    await waitForAll(['Loading...']);
-    expect(root).not.toMatchRenderedOutput('22');
-
-    // Mount
-    await act(() => resolveFakeImport(Add));
-
-    assertConsoleErrorDev(
-      [
-        'Add: Support for defaultProps will be removed from memo components in a future major release. Use JavaScript default parameters instead.',
-      ],
-      {withoutStack: true},
-    );
-
-    expect(root).toMatchRenderedOutput('22');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd inner={false} outer={false} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('0');
-  });
-
   it('resolves props for outer memo component without defaultProps', async () => {
     let Add = props => {
       return props.inner + props.outer;
@@ -1408,52 +1225,6 @@ describe('ReactLazy', () => {
     expect(root).toMatchRenderedOutput('0');
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('resolves props for inner memo component with defaultProps', async () => {
-    const Add = props => {
-      expect(props.innerWithDefault).toBe(42);
-      return props.inner + props.outer;
-    };
-    Add.displayName = 'Add';
-    Add.defaultProps = {
-      innerWithDefault: 42,
-    };
-    const MemoAdd = React.memo(Add);
-    const LazyAdd = lazy(() => fakeImport(MemoAdd));
-    const root = ReactTestRenderer.create(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd inner="2" outer="2" />
-      </Suspense>,
-      {
-        unstable_isConcurrent: true,
-      },
-    );
-
-    await waitForAll(['Loading...']);
-    expect(root).not.toMatchRenderedOutput('22');
-
-    // Mount
-    await act(() => resolveFakeImport(MemoAdd));
-
-    assertConsoleErrorDev(
-      [
-        'Add: Support for defaultProps will be removed from function components in a future major release. Use JavaScript default parameters instead.',
-      ],
-      {withoutStack: true},
-    );
-
-    expect(root).toMatchRenderedOutput('22');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd inner={false} outer={false} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('0');
-  });
-
   it('resolves props for inner memo component without defaultProps', async () => {
     const Add = props => {
       return props.inner + props.outer;
@@ -1487,50 +1258,6 @@ describe('ReactLazy', () => {
     expect(root).toMatchRenderedOutput('0');
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('uses outer resolved props on memo', async () => {
-    let T = props => {
-      return <Text text={props.text} />;
-    };
-    T.defaultProps = {
-      text: 'Inner default text',
-    };
-    T = React.memo(T);
-    const LazyText = lazy(() => fakeImport(T));
-    const root = ReactTestRenderer.create(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyText />
-      </Suspense>,
-      {
-        unstable_isConcurrent: true,
-      },
-    );
-
-    await waitForAll(['Loading...']);
-    expect(root).not.toMatchRenderedOutput('Inner default text');
-
-    // Mount
-    await act(() => resolveFakeImport(T));
-    assertLog(['Inner default text']);
-    assertConsoleErrorDev(
-      [
-        'T: Support for defaultProps will be removed from function components in a future major release. ' +
-          'Use JavaScript default parameters instead.',
-      ],
-      {withoutStack: true},
-    );
-    expect(root).toMatchRenderedOutput('Inner default text');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyText text={null} />
-      </Suspense>,
-    );
-    await waitForAll([null]);
-    expect(root).toMatchRenderedOutput(null);
-  });
-
   it('includes lazy-loaded component in warning stack', async () => {
     const Foo = props => <div>{[<Text text="A" />, <Text text="B" />]}</div>;
     const LazyFoo = lazy(() => {
@@ -1614,150 +1341,6 @@ describe('ReactLazy', () => {
     expect(ref.current).not.toBe(null);
   });
 
-  // Regression test for #14310
-  // @gate !disableDefaultPropsExceptForClasses
-  it('supports defaultProps defined on the memo() return value', async () => {
-    const Add = React.memo(props => {
-      return props.inner + props.outer;
-    });
-    Add.defaultProps = {
-      inner: 2,
-    };
-    const LazyAdd = lazy(() => fakeImport(Add));
-    const root = ReactTestRenderer.create(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={2} />
-      </Suspense>,
-      {
-        unstable_isConcurrent: true,
-      },
-    );
-    await waitForAll(['Loading...']);
-    expect(root).not.toMatchRenderedOutput('4');
-
-    // Mount
-    await act(() => resolveFakeImport(Add));
-    assertConsoleErrorDev(
-      [
-        'Unknown: Support for defaultProps will be removed from memo components in a future major release. ' +
-          'Use JavaScript default parameters instead.',
-      ],
-      {withoutStack: true},
-    );
-    expect(root).toMatchRenderedOutput('4');
-
-    // Update (shallowly equal)
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={2} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('4');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={3} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('5');
-
-    // Update (shallowly equal)
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={3} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('5');
-
-    // Update (explicit props)
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={1} inner={1} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('2');
-
-    // Update (explicit props, shallowly equal)
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={1} inner={1} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('2');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={1} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('3');
-  });
-
-  // @gate !disableDefaultPropsExceptForClasses
-  it('merges defaultProps in the correct order', async () => {
-    let Add = React.memo(props => {
-      return props.inner + props.outer;
-    });
-    Add.defaultProps = {
-      inner: 100,
-    };
-    Add = React.memo(Add);
-    Add.defaultProps = {
-      inner: 2,
-      outer: 0,
-    };
-    const LazyAdd = lazy(() => fakeImport(Add));
-    const root = ReactTestRenderer.create(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={2} />
-      </Suspense>,
-      {
-        unstable_isConcurrent: true,
-      },
-    );
-    await waitForAll(['Loading...']);
-    expect(root).not.toMatchRenderedOutput('4');
-
-    // Mount
-    await act(() => resolveFakeImport(Add));
-    assertConsoleErrorDev(
-      [
-        'Memo: Support for defaultProps will be removed from memo components in a future major release. ' +
-          'Use JavaScript default parameters instead.',
-        'Unknown: Support for defaultProps will be removed from memo components in a future major release. ' +
-          'Use JavaScript default parameters instead.',
-      ],
-      {withoutStack: true},
-    );
-    expect(root).toMatchRenderedOutput('4');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd outer={3} />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('5');
-
-    // Update
-    root.update(
-      <Suspense fallback={<Text text="Loading..." />}>
-        <LazyAdd />
-      </Suspense>,
-    );
-    await waitForAll([]);
-    expect(root).toMatchRenderedOutput('2');
-  });
-
   it('should error with a component stack naming the resolved component', async () => {
     let componentStackMessage;
 
diff --git a/packages/react-reconciler/src/__tests__/ReactMemo-test.js b/packages/react-reconciler/src/__tests__/ReactMemo-test.js
index 02f5e6ef18813..e96dc72e6a13b 100644
--- a/packages/react-reconciler/src/__tests__/ReactMemo-test.js
+++ b/packages/react-reconciler/src/__tests__/ReactMemo-test.js
@@ -373,77 +373,6 @@ describe('memo', () => {
         expect(ReactNoop).toMatchRenderedOutput(<span prop="1!" />);
       });
 
-      // @gate !disableDefaultPropsExceptForClasses
-      it('supports defaultProps defined on the memo() return value', async () => {
-        function Counter({a, b, c, d, e}) {
-          return <Text text={a + b + c + d + e} />;
-        }
-        Counter.defaultProps = {
-          a: 1,
-        };
-        // Note! We intentionally use React.memo() rather than the injected memo().
-        // This tests a synchronous chain of React.memo() without lazy() in the middle.
-        Counter = React.memo(Counter);
-        Counter.defaultProps = {
-          b: 2,
-        };
-        Counter = React.memo(Counter);
-        Counter = React.memo(Counter); // Layer without defaultProps
-        Counter.defaultProps = {
-          c: 3,
-        };
-        Counter = React.memo(Counter);
-        Counter.defaultProps = {
-          d: 4,
-        };
-        // The final layer uses memo() from test fixture (which might be lazy).
-        Counter = memo(Counter);
-
-        await act(() => {
-          ReactNoop.render(
-            <Suspense fallback={<Text text="Loading..." />}>
-              <Counter e={5} />
-            </Suspense>,
-          );
-        });
-        assertLog(['Loading...', 15]);
-        if (label === 'lazy') {
-          assertConsoleErrorDev(
-            [
-              'Counter: Support for defaultProps will be removed from memo components in a future major release. ' +
-                'Use JavaScript default parameters instead.',
-            ],
-            {withoutStack: true},
-          );
-        } else {
-          assertConsoleErrorDev([
-            'Counter: Support for defaultProps will be removed from memo components in a future major release. ' +
-              'Use JavaScript default parameters instead.\n' +
-              '    in Indirection (at **)',
-          ]);
-        }
-
-        expect(ReactNoop).toMatchRenderedOutput(<span prop={15} />);
-
-        // Should bail out because props have not changed
-        ReactNoop.render(
-          <Suspense>
-            <Counter e={5} />
-          </Suspense>,
-        );
-        await waitForAll([]);
-        expect(ReactNoop).toMatchRenderedOutput(<span prop={15} />);
-
-        // Should update because count prop changed
-        ReactNoop.render(
-          <Suspense>
-            <Counter e={10} />
-          </Suspense>,
-        );
-        await waitForAll([20]);
-        expect(ReactNoop).toMatchRenderedOutput(<span prop={20} />);
-      });
-
       it('warns if the first argument is undefined', () => {
         memo();
         assertConsoleErrorDev(
@@ -466,46 +395,6 @@ describe('memo', () => {
         );
       });
 
-      // @gate !disableDefaultPropsExceptForClasses
-      it('handles nested defaultProps declarations', async () => {
-        function Inner(props) {
-          return props.inner + props.middle + props.outer;
-        }
-        Inner.defaultProps = {inner: 1};
-        const Middle = React.memo(Inner);
-        Middle.defaultProps = {middle: 10};
-        const Outer = React.memo(Middle);
-        Outer.defaultProps = {outer: 100};
-
-        const root = ReactNoop.createRoot();
-        await act(() => {
-          root.render(
-            <div>
-              <Outer />
-            </div>,
-          );
-        });
-        assertConsoleErrorDev(
-          [
-            'Inner: ' +
-              'Support for defaultProps will be removed from memo components in a future major release. ' +
-              'Use JavaScript default parameters instead.',
-          ],
-          {withoutStack: true},
-        );
-        expect(root).toMatchRenderedOutput(<div>111</div>);
-
-        await act(async () => {
-          root.render(
-            <div>
-              <Outer inner="2" middle="3" outer="4" />
-            </div>,
-          );
-          await waitForAll([]);
-        });
-        expect(root).toMatchRenderedOutput(<div>234</div>);
-      });
-
       it('does not drop lower priority state updates when bailing out at higher pri (simple)', async () => {
         const {useState} = React;
 
diff --git a/packages/react-server/src/ReactFizzServer.js b/packages/react-server/src/ReactFizzServer.js
index 2f58c14e5df2f..732dc1067872f 100644
--- a/packages/react-server/src/ReactFizzServer.js
+++ b/packages/react-server/src/ReactFizzServer.js
@@ -178,7 +178,6 @@ import {
   enableScopeAPI,
   enablePostpone,
   enableHalt,
-  disableDefaultPropsExceptForClasses,
   enableAsyncIterableChildren,
   enableViewTransition,
   enableFizzBlockingRender,
@@ -2399,12 +2398,7 @@ export function resolveClassComponentProps(
 
   // Resolve default props.
   const defaultProps = Component.defaultProps;
-  if (
-    defaultProps &&
-    // If disableDefaultPropsExceptForClasses is true, we always resolve
-    // default props here, rather than in the JSX runtime.
-    disableDefaultPropsExceptForClasses
-  ) {
+  if (defaultProps) {
     // We may have already copied the props object above to remove ref. If so,
     // we can modify that. Otherwise, copy the props object with Object.assign.
     if (newProps === baseProps) {
@@ -2453,7 +2447,6 @@ const didWarnAboutContextTypes: {[string]: boolean} = {};
 const didWarnAboutContextTypeOnFunctionComponent: {[string]: boolean} = {};
 const didWarnAboutGetDerivedStateOnFunctionComponent: {[string]: boolean} = {};
 let didWarnAboutReassigningProps = false;
-const didWarnAboutDefaultPropsOnFunctionComponent: {[string]: boolean} = {};
 let didWarnAboutGenerators = false;
 let didWarnAboutMaps = false;
 
@@ -2610,22 +2603,6 @@ function validateFunctionComponentInDev(Component: any): void {
       );
     }
 
-    if (
-      !disableDefaultPropsExceptForClasses &&
-      Component.defaultProps !== undefined
-    ) {
-      const componentName = getComponentNameFromType(Component) || 'Unknown';
-
-      if (!didWarnAboutDefaultPropsOnFunctionComponent[componentName]) {
-        console.error(
-          '%s: Support for defaultProps will be removed from function components ' +
-            'in a future major release. Use JavaScript default parameters instead.',
-          componentName,
-        );
-        didWarnAboutDefaultPropsOnFunctionComponent[componentName] = true;
-      }
-    }
-
     if (typeof Component.getDerivedStateFromProps === 'function') {
       const componentName = getComponentNameFromType(Component) || 'Unknown';
 
@@ -2655,29 +2632,6 @@ function validateFunctionComponentInDev(Component: any): void {
   }
 }
 
-function resolveDefaultPropsOnNonClassComponent(
-  Component: any,
-  baseProps: Object,
-): Object {
-  if (disableDefaultPropsExceptForClasses) {
-    // Support for defaultProps is removed in React 19 for all types
-    // except classes.
-    return baseProps;
-  }
-  if (Component && Component.defaultProps) {
-    // Resolve default props. Taken from ReactElement
-    const props = assign({}, baseProps);
-    const defaultProps = Component.defaultProps;
-    for (const propName in defaultProps) {
-      if (props[propName] === undefined) {
-        props[propName] = defaultProps[propName];
-      }
-    }
-    return props;
-  }
-  return baseProps;
-}
-
 function renderForwardRef(
   request: Request,
   task: Task,
@@ -2735,11 +2689,7 @@ function renderMemo(
   ref: any,
 ): void {
   const innerType = type.type;
-  const resolvedProps = resolveDefaultPropsOnNonClassComponent(
-    innerType,
-    props,
-  );
-  renderElement(request, task, keyPath, innerType, resolvedProps, ref);
+  renderElement(request, task, keyPath, innerType, props, ref);
 }
 
 function renderContextConsumer(
@@ -2819,11 +2769,7 @@ function renderLazyComponent(
     // eslint-disable-next-line no-throw-literal
     throw null;
   }
-  const resolvedProps = resolveDefaultPropsOnNonClassComponent(
-    Component,
-    props,
-  );
-  renderElement(request, task, keyPath, Component, resolvedProps, ref);
+  renderElement(request, task, keyPath, Component, props, ref);
 }
 
 function renderActivity(
diff --git a/packages/react/src/ReactLazy.js b/packages/react/src/ReactLazy.js
index d1d1088aaeb0d..2ac29c87774ec 100644
--- a/packages/react/src/ReactLazy.js
+++ b/packages/react/src/ReactLazy.js
@@ -10,7 +10,6 @@
 import type {Wakeable, Thenable, ReactDebugInfo} from 'shared/ReactTypes';
 
 import {REACT_LAZY_TYPE} from 'shared/ReactSymbols';
-import {disableDefaultPropsExceptForClasses} from 'shared/ReactFeatureFlags';
 
 const Uninitialized = -1;
 const Pending = 0;
@@ -141,35 +140,5 @@ export function lazy<T>(
     _init: lazyInitializer,
   };
 
-  if (!disableDefaultPropsExceptForClasses) {
-    if (__DEV__) {
-      // In production, this would just set it on the object.
-      let defaultProps;
-      // $FlowFixMe[prop-missing]
-      Object.defineProperties(lazyType, {
-        defaultProps: {
-          configurable: true,
-          get() {
-            return defaultProps;
-          },
-          // $FlowFixMe[missing-local-annot]
-          set(newDefaultProps) {
-            console.error(
-              'It is not supported to assign `defaultProps` to ' +
-                'a lazy component import. Either specify them where the component ' +
-                'is defined, or create a wrapping component around it.',
-            );
-            defaultProps = newDefaultProps;
-            // Match production behavior more closely:
-            // $FlowFixMe[prop-missing]
-            Object.defineProperty(lazyType, 'defaultProps', {
-              enumerable: true,
-            });
-          },
-        },
-      });
-    }
-  }
-
   return lazyType;
 }
diff --git a/packages/react/src/__tests__/ReactElementClone-test.js b/packages/react/src/__tests__/ReactElementClone-test.js
index b2e791f8268c9..81da2a6f3942a 100644
--- a/packages/react/src/__tests__/ReactElementClone-test.js
+++ b/packages/react/src/__tests__/ReactElementClone-test.js
@@ -291,28 +291,6 @@ describe('ReactElementClone', () => {
     );
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('should normalize props with default values', () => {
-    class Component extends React.Component {
-      render() {
-        return <span />;
-      }
-    }
-    Component.defaultProps = {prop: 'testKey'};
-
-    const instance = React.createElement(Component);
-    const clonedInstance = React.cloneElement(instance, {prop: undefined});
-    expect(clonedInstance.props.prop).toBe('testKey');
-    const clonedInstance2 = React.cloneElement(instance, {prop: null});
-    expect(clonedInstance2.props.prop).toBe(null);
-
-    const instance2 = React.createElement(Component, {prop: 'newTestKey'});
-    const cloneInstance3 = React.cloneElement(instance2, {prop: undefined});
-    expect(cloneInstance3.props.prop).toBe('testKey');
-    const cloneInstance4 = React.cloneElement(instance2, {});
-    expect(cloneInstance4.props.prop).toBe('newTestKey');
-  });
-
   it('warns for keys for arrays of elements in rest args', async () => {
     const root = ReactDOMClient.createRoot(document.createElement('div'));
     await act(() => {
diff --git a/packages/react/src/__tests__/forwardRef-test.js b/packages/react/src/__tests__/forwardRef-test.js
index aa151fc6d1c81..b163ac0025e5f 100644
--- a/packages/react/src/__tests__/forwardRef-test.js
+++ b/packages/react/src/__tests__/forwardRef-test.js
@@ -76,45 +76,6 @@ describe('forwardRef', () => {
     expect(ref.current).toBe(null);
   });
 
-  // @gate !disableDefaultPropsExceptForClasses
-  it('should support defaultProps', async () => {
-    function FunctionComponent({forwardedRef, optional, required}) {
-      return (
-        <div ref={forwardedRef}>
-          {optional}
-          {required}
-        </div>
-      );
-    }
-
-    const RefForwardingComponent = React.forwardRef(
-      function NamedFunction(props, ref) {
-        return <FunctionComponent {...props} forwardedRef={ref} />;
-      },
-    );
-    RefForwardingComponent.defaultProps = {
-      optional: 'default',
-    };
-
-    const ref = React.createRef();
-
-    ReactNoop.render(
-      <RefForwardingComponent ref={ref} optional="foo" required="bar" />,
-    );
-    await waitForAll([]);
-    expect(ref.current.children).toEqual([
-      {text: 'foo', hidden: false},
-      {text: 'bar', hidden: false},
-    ]);
-
-    ReactNoop.render(<RefForwardingComponent ref={ref} required="foo" />);
-    await waitForAll([]);
-    expect(ref.current.children).toEqual([
-      {text: 'default', hidden: false},
-      {text: 'foo', hidden: false},
-    ]);
-  });
-
   it('should warn if not provided a callback during creation', () => {
     React.forwardRef(undefined);
     assertConsoleErrorDev(
diff --git a/packages/react/src/jsx/ReactJSXElement.js b/packages/react/src/jsx/ReactJSXElement.js
index a20378a93cb4d..e5b2671a6eae9 100644
--- a/packages/react/src/jsx/ReactJSXElement.js
+++ b/packages/react/src/jsx/ReactJSXElement.js
@@ -16,10 +16,7 @@ import {
 } from 'shared/ReactSymbols';
 import {checkKeyStringCoercion} from 'shared/CheckStringCoercion';
 import isArray from 'shared/isArray';
-import {
-  disableDefaultPropsExceptForClasses,
-  ownerStackLimit,
-} from 'shared/ReactFeatureFlags';
+import {ownerStackLimit} from 'shared/ReactFeatureFlags';
 
 const createTask =
   // eslint-disable-next-line react-internal/no-production-logging
@@ -351,18 +348,6 @@ export function jsxProd(type, config, maybeKey) {
     }
   }
 
-  if (!disableDefaultPropsExceptForClasses) {
-    // Resolve default props
-    if (type && type.defaultProps) {
-      const defaultProps = type.defaultProps;
-      for (const propName in defaultProps) {
-        if (props[propName] === undefined) {
-          props[propName] = defaultProps[propName];
-        }
-      }
-    }
-  }
-
   return ReactElement(
     type,
     key,
@@ -598,18 +583,6 @@ function jsxDEVImpl(
       }
     }
 
-    if (!disableDefaultPropsExceptForClasses) {
-      // Resolve default props
-      if (type && type.defaultProps) {
-        const defaultProps = type.defaultProps;
-        for (const propName in defaultProps) {
-          if (props[propName] === undefined) {
-            props[propName] = defaultProps[propName];
-          }
-        }
-      }
-    }
-
     if (key) {
       const displayName =
         typeof type === 'function'
@@ -817,14 +790,6 @@ export function cloneElement(element, config, children) {
     }
 
     // Remaining properties override existing props
-    let defaultProps;
-    if (
-      !disableDefaultPropsExceptForClasses &&
-      element.type &&
-      element.type.defaultProps
-    ) {
-      defaultProps = element.type.defaultProps;
-    }
     for (propName in config) {
       if (
         hasOwnProperty.call(config, propName) &&
@@ -843,16 +808,7 @@ export function cloneElement(element, config, children) {
         // backwards compatibility.
         !(propName === 'ref' && config.ref === undefined)
       ) {
-        if (
-          !disableDefaultPropsExceptForClasses &&
-          config[propName] === undefined &&
-          defaultProps !== undefined
-        ) {
-          // Resolve default props
-          props[propName] = defaultProps[propName];
-        } else {
-          props[propName] = config[propName];
-        }
+        props[propName] = config[propName];
       }
     }
   }
diff --git a/packages/shared/ReactFeatureFlags.js b/packages/shared/ReactFeatureFlags.js
index a56cc2582e5e0..e247562b690cc 100644
--- a/packages/shared/ReactFeatureFlags.js
+++ b/packages/shared/ReactFeatureFlags.js
@@ -37,9 +37,6 @@ export const favorSafetyOverHydrationPerf = true;
 // Need to remove didTimeout argument from Scheduler before landing
 export const disableSchedulerTimeoutInWorkLoop = false;
 
-// TODO: Land at Meta before removing.
-export const disableDefaultPropsExceptForClasses = true;
-
 // -----------------------------------------------------------------------------
 // Slated for removal in the future (significant effort)
 //
diff --git a/packages/shared/forks/ReactFeatureFlags.native-fb.js b/packages/shared/forks/ReactFeatureFlags.native-fb.js
index 09f6b62983208..0c662271833df 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-fb.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-fb.js
@@ -33,7 +33,6 @@ export const {
 // The rest of the flags are static for better dead code elimination.
 export const disableClientCache = true;
 export const disableCommentsAsDOMContainers = true;
-export const disableDefaultPropsExceptForClasses = true;
 export const disableInputAttributeSyncing = false;
 export const disableLegacyContext = false;
 export const disableLegacyContextForFunctionComponents = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.native-oss.js b/packages/shared/forks/ReactFeatureFlags.native-oss.js
index 6893a3215b17d..ed372097cb4be 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-oss.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-oss.js
@@ -18,7 +18,6 @@ import typeof * as ExportsType from './ReactFeatureFlags.native-oss';
 export const alwaysThrottleRetries = false;
 export const disableClientCache = true;
 export const disableCommentsAsDOMContainers = true;
-export const disableDefaultPropsExceptForClasses = true;
 export const disableInputAttributeSyncing = false;
 export const disableLegacyContext = true;
 export const disableLegacyContextForFunctionComponents = true;
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
index c0a909ba5ce8a..66514e7697534 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
@@ -89,7 +89,6 @@ export const disableLegacyMode = true;
 export const disableLegacyContext = true;
 export const disableLegacyContextForFunctionComponents = true;
 export const enableReactTestRendererWarning = true;
-export const disableDefaultPropsExceptForClasses = true;
 
 export const enableObjectFiber = false;
 
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
index 209fbd4b8ceb0..ef912457ef8fb 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
@@ -63,8 +63,6 @@ export const enableInfiniteRenderLoopDetection = false;
 export const enableReactTestRendererWarning = false;
 export const disableLegacyMode = true;
 
-export const disableDefaultPropsExceptForClasses = true;
-
 export const renameElementSymbol = false;
 
 export const enableObjectFiber = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.www-dynamic.js b/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
index eeccf763ca364..2f4da5916e860 100644
--- a/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
+++ b/packages/shared/forks/ReactFeatureFlags.www-dynamic.js
@@ -14,7 +14,6 @@
 // with the __VARIANT__ set to `true`, and once set to `false`.
 
 export const alwaysThrottleRetries = __VARIANT__;
-export const disableDefaultPropsExceptForClasses = __VARIANT__;
 export const disableLegacyContextForFunctionComponents = __VARIANT__;
 export const disableSchedulerTimeoutInWorkLoop = __VARIANT__;
 export const enableHiddenSubtreeInsertionEffectCleanup = __VARIANT__;
diff --git a/packages/shared/forks/ReactFeatureFlags.www.js b/packages/shared/forks/ReactFeatureFlags.www.js
index 29bb652fd74ea..4acdf65a92274 100644
--- a/packages/shared/forks/ReactFeatureFlags.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.www.js
@@ -16,7 +16,6 @@ const dynamicFeatureFlags: DynamicFeatureFlags = require('ReactFeatureFlags');
 
 export const {
   alwaysThrottleRetries,
-  disableDefaultPropsExceptForClasses,
   disableLegacyContextForFunctionComponents,
   disableSchedulerTimeoutInWorkLoop,
   enableHiddenSubtreeInsertionEffectCleanup,