diff --git a/.changeset/giant-phones-melt.md b/.changeset/giant-phones-melt.md
new file mode 100644
index 0000000000..1506e2d0f3
--- /dev/null
+++ b/.changeset/giant-phones-melt.md
@@ -0,0 +1,5 @@
+---
+'@backstage/frontend-test-utils': minor
+---
+
+**BREAKING**: Removed deprecated `setupRequestMockHandlers` which was replaced by `registerMswTestHooks`.
diff --git a/.changeset/honest-ravens-stare.md b/.changeset/honest-ravens-stare.md
new file mode 100644
index 0000000000..7b78ce4357
--- /dev/null
+++ b/.changeset/honest-ravens-stare.md
@@ -0,0 +1,7 @@
+---
+'@backstage/frontend-defaults': minor
+'@backstage/frontend-app-api': minor
+'@backstage/core-compat-api': minor
+---
+
+**BREAKING**: Dropped support for the removed opaque `@backstage/ExtensionOverrides` and `@backstage/BackstagePlugin` types.
diff --git a/.changeset/itchy-shoes-rest.md b/.changeset/itchy-shoes-rest.md
new file mode 100644
index 0000000000..3e40fab36e
--- /dev/null
+++ b/.changeset/itchy-shoes-rest.md
@@ -0,0 +1,5 @@
+---
+'@backstage/frontend-plugin-api': minor
+---
+
+**BREAKING**: Removed the deprecated `ExtensionOverrides` and `FrontendFeature` types.
diff --git a/.changeset/lazy-deers-dance.md b/.changeset/lazy-deers-dance.md
new file mode 100644
index 0000000000..80adcbaa14
--- /dev/null
+++ b/.changeset/lazy-deers-dance.md
@@ -0,0 +1,5 @@
+---
+'@backstage/frontend-plugin-api': minor
+---
+
+**BREAKING**: Removed deprecated variant of `createExtensionDataRef` where the ID is passed directly.
diff --git a/packages/core-compat-api/report.api.md b/packages/core-compat-api/report.api.md
index 50aec1f646..9f7582db03 100644
--- a/packages/core-compat-api/report.api.md
+++ b/packages/core-compat-api/report.api.md
@@ -14,7 +14,6 @@ import { AppTheme } from '@backstage/core-plugin-api';
 import { BackstagePlugin } from '@backstage/core-plugin-api';
 import { ComponentType } from 'react';
 import { ExtensionDefinition } from '@backstage/frontend-plugin-api';
-import { ExtensionOverrides } from '@backstage/frontend-plugin-api';
 import { ExternalRouteRef } from '@backstage/core-plugin-api';
 import { ExternalRouteRef as ExternalRouteRef_2 } from '@backstage/frontend-plugin-api';
 import { FeatureFlag } from '@backstage/core-plugin-api';
@@ -34,7 +33,7 @@ export function compatWrapper(element: ReactNode): React_2.JSX.Element;
 // @public (undocumented)
 export function convertLegacyApp(
   rootElement: React_2.JSX.Element,
-): (FrontendPlugin | FrontendModule | ExtensionOverrides)[];
+): (FrontendPlugin | FrontendModule)[];
 
 // @public (undocumented)
 export function convertLegacyAppOptions(options?: {
diff --git a/packages/core-compat-api/src/convertLegacyApp.ts b/packages/core-compat-api/src/convertLegacyApp.ts
index f098d090ed..52efc96ee2 100644
--- a/packages/core-compat-api/src/convertLegacyApp.ts
+++ b/packages/core-compat-api/src/convertLegacyApp.ts
@@ -26,7 +26,6 @@ import {
   FrontendPlugin,
   coreExtensionData,
   createExtension,
-  ExtensionOverrides,
   createExtensionInput,
   createFrontendModule,
 } from '@backstage/frontend-plugin-api';
@@ -63,7 +62,7 @@ function selectChildren(
 /** @public */
 export function convertLegacyApp(
   rootElement: React.JSX.Element,
-): (FrontendPlugin | FrontendModule | ExtensionOverrides)[] {
+): (FrontendPlugin | FrontendModule)[] {
   if (getComponentData(rootElement, 'core.type') === 'FlatRoutes') {
     return collectLegacyRoutes(rootElement);
   }
diff --git a/packages/frontend-app-api/report.api.md b/packages/frontend-app-api/report.api.md
index d3c2045f85..bdc9caaa0b 100644
--- a/packages/frontend-app-api/report.api.md
+++ b/packages/frontend-app-api/report.api.md
@@ -41,13 +41,5 @@ export function createSpecializedApp(options?: {
 };
 
 // @public (undocumented)
-export type FrontendFeature =
-  | FrontendPlugin
-  | FrontendModule
-  | {
-      $$type: '@backstage/ExtensionOverrides';
-    }
-  | {
-      $$type: '@backstage/BackstagePlugin';
-    };
+export type FrontendFeature = FrontendPlugin | FrontendModule;
 ```
diff --git a/packages/frontend-app-api/src/wiring/types.ts b/packages/frontend-app-api/src/wiring/types.ts
index 18d9c51d0e..6699f1c272 100644
--- a/packages/frontend-app-api/src/wiring/types.ts
+++ b/packages/frontend-app-api/src/wiring/types.ts
@@ -18,12 +18,7 @@ import { FrontendModule, FrontendPlugin } from '@backstage/frontend-plugin-api';
 import { BackstageRouteObject } from '../routing/types';
 
 /** @public  */
-export type FrontendFeature =
-  | FrontendPlugin
-  | FrontendModule
-  // TODO(blam): This is just forwards backwards compatibility, remove after v1.31.0
-  | { $$type: '@backstage/ExtensionOverrides' }
-  | { $$type: '@backstage/BackstagePlugin' };
+export type FrontendFeature = FrontendPlugin | FrontendModule;
 
 /** @internal */
 export type RouteInfo = {
diff --git a/packages/frontend-defaults/src/discovery.ts b/packages/frontend-defaults/src/discovery.ts
index e82f2acfda..398d8a204f 100644
--- a/packages/frontend-defaults/src/discovery.ts
+++ b/packages/frontend-defaults/src/discovery.ts
@@ -88,11 +88,7 @@ function isBackstageFeature(obj: unknown): obj is FrontendFeature {
   if (obj !== null && typeof obj === 'object' && '$$type' in obj) {
     return (
       obj.$$type === '@backstage/FrontendPlugin' ||
-      obj.$$type === '@backstage/FrontendModule' ||
-      // TODO: Remove this once the old plugin type and extension overrides
-      // are no longer supported
-      obj.$$type === '@backstage/BackstagePlugin' ||
-      obj.$$type === '@backstage/ExtensionOverrides'
+      obj.$$type === '@backstage/FrontendModule'
     );
   }
   return false;
diff --git a/packages/frontend-plugin-api/report.api.md b/packages/frontend-plugin-api/report.api.md
index 52d0276952..3ae6451627 100644
--- a/packages/frontend-plugin-api/report.api.md
+++ b/packages/frontend-plugin-api/report.api.md
@@ -610,11 +610,6 @@ export type CreateExtensionBlueprintOptions<
   dataRefs?: TDataRefs;
 } & VerifyExtensionFactoryOutput<UOutput, UFactoryOutput>;
 
-// @public @deprecated (undocumented)
-export function createExtensionDataRef<TData>(
-  id: string,
-): ConfigurableExtensionDataRef<TData, string>;
-
 // @public (undocumented)
 export function createExtensionDataRef<TData>(): {
   with<TId extends string>(options: {
@@ -1212,12 +1207,6 @@ export interface ExtensionInput<
   }>;
 }
 
-// @public (undocumented)
-export interface ExtensionOverrides {
-  // (undocumented)
-  readonly $$type: '@backstage/ExtensionOverrides';
-}
-
 // @public
 export interface ExternalRouteRef<
   TParams extends AnyRouteRefParams = AnyRouteRefParams,
@@ -1247,9 +1236,6 @@ export { FetchApi };
 
 export { fetchApiRef };
 
-// @public @deprecated (undocumented)
-export type FrontendFeature = FrontendPlugin | ExtensionOverrides;
-
 // @public (undocumented)
 export interface FrontendModule {
   // (undocumented)
diff --git a/packages/frontend-plugin-api/src/wiring/createExtensionDataRef.test.ts b/packages/frontend-plugin-api/src/wiring/createExtensionDataRef.test.ts
index 4b652298f1..b5acf78384 100644
--- a/packages/frontend-plugin-api/src/wiring/createExtensionDataRef.test.ts
+++ b/packages/frontend-plugin-api/src/wiring/createExtensionDataRef.test.ts
@@ -29,15 +29,6 @@ describe('createExtensionDataRef', () => {
     expect(String(refOptional)).toBe('ExtensionDataRef{id=foo,optional=true}');
   });
 
-  it('can be created and read in the deprecated way', () => {
-    const ref = createExtensionDataRef('foo');
-    expect(ref.id).toBe('foo');
-    expect(String(ref)).toBe('ExtensionDataRef{id=foo,optional=false}');
-    const refOptional = ref.optional();
-    expect(refOptional.id).toBe('foo');
-    expect(String(refOptional)).toBe('ExtensionDataRef{id=foo,optional=true}');
-  });
-
   it('can be used to encapsulate a value', () => {
     const ref = createExtensionDataRef<string>().with({ id: 'foo' });
     const val: ExtensionDataValue<string, 'foo'> = ref('hello');
diff --git a/packages/frontend-plugin-api/src/wiring/createExtensionDataRef.ts b/packages/frontend-plugin-api/src/wiring/createExtensionDataRef.ts
index 80413c1688..94acb192a8 100644
--- a/packages/frontend-plugin-api/src/wiring/createExtensionDataRef.ts
+++ b/packages/frontend-plugin-api/src/wiring/createExtensionDataRef.ts
@@ -60,26 +60,12 @@ export interface ConfigurableExtensionDataRef<
   (t: TData): ExtensionDataValue<TData, TId>;
 }
 
-/**
- * @public
- * @deprecated Use the following form instead: `createExtensionDataRef<Type>().with({ id: 'core.foo' })`
- */
-export function createExtensionDataRef<TData>(
-  id: string,
-): ConfigurableExtensionDataRef<TData, string>;
 /** @public */
 export function createExtensionDataRef<TData>(): {
   with<TId extends string>(options: {
     id: TId;
   }): ConfigurableExtensionDataRef<TData, TId>;
-};
-export function createExtensionDataRef<TData>(id?: string):
-  | ConfigurableExtensionDataRef<TData, string>
-  | {
-      with<TId extends string>(options: {
-        id: TId;
-      }): ConfigurableExtensionDataRef<TData, TId>;
-    } {
+} {
   const createRef = <TId extends string>(refId: TId) =>
     Object.assign(
       (value: TData): ExtensionDataValue<TData, TId> => ({
@@ -103,9 +89,6 @@ export function createExtensionDataRef<TData>(id?: string):
         },
       } as ConfigurableExtensionDataRef<TData, TId, { optional?: true }>,
     );
-  if (id) {
-    return createRef(id);
-  }
   return {
     with<TId extends string>(options: { id: TId }) {
       return createRef(options.id);
diff --git a/packages/frontend-plugin-api/src/wiring/index.ts b/packages/frontend-plugin-api/src/wiring/index.ts
index 6dec88b5f4..b5cefc75fb 100644
--- a/packages/frontend-plugin-api/src/wiring/index.ts
+++ b/packages/frontend-plugin-api/src/wiring/index.ts
@@ -51,9 +51,7 @@ export {
   type AnyRoutes,
   type AnyExternalRoutes,
   type ExtensionDataContainer,
-  type ExtensionOverrides,
   type FeatureFlagConfig,
-  type FrontendFeature,
   type ExtensionFactoryMiddleware,
 } from './types';
 export {
diff --git a/packages/frontend-plugin-api/src/wiring/types.ts b/packages/frontend-plugin-api/src/wiring/types.ts
index 3aba32d9fc..6d3e7a4abd 100644
--- a/packages/frontend-plugin-api/src/wiring/types.ts
+++ b/packages/frontend-plugin-api/src/wiring/types.ts
@@ -22,7 +22,6 @@ import {
   ExtensionDataRef,
   ExtensionDataValue,
 } from './createExtensionDataRef';
-import { FrontendPlugin } from './createFrontendPlugin';
 import { ApiHolder, AppNode } from '../apis';
 
 /**
@@ -48,17 +47,6 @@ export type ExtensionMap<
   get<TId extends keyof TExtensionMap>(id: TId): TExtensionMap[TId];
 };
 
-/** @public */
-export interface ExtensionOverrides {
-  readonly $$type: '@backstage/ExtensionOverrides';
-}
-
-/**
- * @public
- * @deprecated import from {@link @backstage/frontend-app-api#FrontendFeature} instead
- */
-export type FrontendFeature = FrontendPlugin | ExtensionOverrides;
-
 /** @public */
 export type ExtensionDataContainer<UExtensionData extends AnyExtensionDataRef> =
   Iterable<
diff --git a/packages/frontend-test-utils/report.api.md b/packages/frontend-test-utils/report.api.md
index fd6aba0223..e14c971419 100644
--- a/packages/frontend-test-utils/report.api.md
+++ b/packages/frontend-test-utils/report.api.md
@@ -120,13 +120,6 @@ export function renderInTestApp(
   options?: TestAppOptions,
 ): RenderResult;
 
-// @public @deprecated (undocumented)
-export function setupRequestMockHandlers(worker: {
-  listen: (t: any) => void;
-  close: () => void;
-  resetHandlers: () => void;
-}): void;
-
 export { TestApiProvider };
 
 export { TestApiProviderProps };
diff --git a/packages/frontend-test-utils/src/deprecated.ts b/packages/frontend-test-utils/src/deprecated.ts
deleted file mode 100644
index 1b67f73e6b..0000000000
--- a/packages/frontend-test-utils/src/deprecated.ts
+++ /dev/null
@@ -1,29 +0,0 @@
-/*
- * Copyright 2024 The Backstage Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-import { registerMswTestHooks } from '@backstage/test-utils';
-
-/**
- * @public
- * @deprecated Use `registerMswTestHooks` from `@backstage/frontend-test-utils` instead.
- */
-export function setupRequestMockHandlers(worker: {
-  listen: (t: any) => void;
-  close: () => void;
-  resetHandlers: () => void;
-}): void {
-  registerMswTestHooks(worker);
-}
diff --git a/packages/frontend-test-utils/src/index.ts b/packages/frontend-test-utils/src/index.ts
index 20f393706e..cab66895e0 100644
--- a/packages/frontend-test-utils/src/index.ts
+++ b/packages/frontend-test-utils/src/index.ts
@@ -20,7 +20,6 @@
  * Contains utilities that can be used when testing frontend features such as extensions.
  */
 
-export * from './deprecated';
 export * from './apis';
 export * from './app';