diff --git a/packages/react-native/scripts/spm/__tests__/generate-spm-autolinking-test.js b/packages/react-native/scripts/spm/__tests__/generate-spm-autolinking-test.js
index ea32e11dbc0..8736964a712 100644
--- a/packages/react-native/scripts/spm/__tests__/generate-spm-autolinking-test.js
+++ b/packages/react-native/scripts/spm/__tests__/generate-spm-autolinking-test.js
@@ -1179,6 +1179,137 @@ describe('main() — autolinking plugin host exemption', () => {
   );
 });
 
+// ---------------------------------------------------------------------------
+// main() — spm.modules name validation
+//
+// App-local module names land in the manifest exactly as written, so they need
+// the checks an autolinked dep's Swift name gets: a valid identifier, not one
+// of React Native's reserved names, and unique across modules and deps.
+// ---------------------------------------------------------------------------
+
+describe('main() — spm.modules names', () => {
+  let created = [];
+  let spies = [];
+
+  beforeEach(() => {
+    for (const m of ['log', 'warn', 'error']) {
+      spies.push(jest.spyOn(console, m).mockImplementation(() => {}));
+    }
+  });
+
+  afterEach(() => {
+    for (const s of spies) s.mockRestore();
+    spies = [];
+    for (const d of created) fs.rmSync(d, {recursive: true, force: true});
+    created = [];
+  });
+
+  // App fixture whose react-native.config.js declares `spm.modules`, plus an
+  // optional autolinked dep (for the module-vs-dep collision case).
+  function buildApp({modules, dep}) {
+    const appRoot = fs.mkdtempSync(path.join(os.tmpdir(), 'spm-modules-'));
+    created.push(appRoot);
+    const rnRoot = path.join(appRoot, 'rn');
+    fs.mkdirSync(rnRoot, {recursive: true});
+    fs.writeFileSync(
+      path.join(appRoot, 'package.json'),
+      JSON.stringify({name: 'app'}),
+    );
+    for (const mod of modules) {
+      const modDir = path.join(appRoot, mod.path);
+      fs.mkdirSync(modDir, {recursive: true});
+      fs.writeFileSync(path.join(modDir, 'Module.mm'), '// native source\n');
+    }
+    fs.writeFileSync(
+      path.join(appRoot, 'react-native.config.js'),
+      `module.exports = ${JSON.stringify({spm: {modules}})};\n`,
+    );
+    const dependencies = {};
+    if (dep != null) {
+      const depDir = path.join(appRoot, 'node_modules', dep.name);
+      fs.mkdirSync(path.join(depDir, 'ios'), {recursive: true});
+      fs.writeFileSync(
+        path.join(depDir, 'ios', 'Dep.mm'),
+        '// native source\n',
+      );
+      fs.writeFileSync(
+        path.join(depDir, 'Package.swift'),
+        '// swift-tools-version: 6.0\n',
+      );
+      dependencies[dep.name] = {root: depDir, platforms: {ios: {}}};
+    }
+    const autolinkDir = path.join(appRoot, 'build', 'generated', 'autolinking');
+    fs.mkdirSync(autolinkDir, {recursive: true});
+    fs.writeFileSync(
+      path.join(autolinkDir, 'autolinking.json'),
+      JSON.stringify({dependencies}),
+    );
+    return {appRoot, rnRoot};
+  }
+
+  const run = ({appRoot, rnRoot}) =>
+    main(['--app-root', appRoot, '--react-native-root', rnRoot]);
+
+  it('accepts a normal module name', () => {
+    const app = buildApp({
+      modules: [{name: 'MyNativeModule', path: 'ios/MyNativeModule'}],
+    });
+    expect(() => run(app)).not.toThrow();
+  });
+
+  it('rejects a module named after a reserved React Native name', () => {
+    const app = buildApp({
+      modules: [{name: 'ReactNative', path: 'ios/MyNativeModule'}],
+    });
+    expect(() => run(app)).toThrow(SpmNameCollisionError);
+    expect(() => run(app)).toThrow(
+      /the 'spm.modules' entry 'ReactNative' resolves to 'ReactNative', which React Native reserves/,
+    );
+    expect(() => run(app)).toThrow(/'spm\.modules'\.$/);
+  });
+
+  it('rejects a reserved product name in any casing', () => {
+    const app = buildApp({
+      modules: [{name: 'reactheaders', path: 'ios/MyNativeModule'}],
+    });
+    expect(() => run(app)).toThrow(SpmNameCollisionError);
+    expect(() => run(app)).toThrow(
+      /the 'spm\.modules' entry 'reactheaders' resolves to 'reactheaders', which differs from React Native's reserved 'ReactHeaders' only in case/,
+    );
+  });
+
+  it('rejects a module name that is not a valid Swift identifier', () => {
+    const app = buildApp({
+      modules: [{name: 'My Module', path: 'ios/MyNativeModule'}],
+    });
+    expect(() => run(app)).toThrow(/invalid 'spm.modules' name "My Module"/);
+  });
+
+  it('rejects two modules resolving to the same name', () => {
+    const app = buildApp({
+      modules: [
+        {name: 'Shared', path: 'ios/one'},
+        {name: 'shared', path: 'ios/two'},
+      ],
+    });
+    expect(() => run(app)).toThrow(SpmNameCollisionError);
+    expect(() => run(app)).toThrow(
+      /the 'spm.modules' entry 'shared' differs from the existing target 'Shared' only in case/,
+    );
+  });
+
+  it('rejects a module colliding with an autolinked dep', () => {
+    const app = buildApp({
+      modules: [{name: 'ReactNativeFoo', path: 'ios/MyNativeModule'}],
+      dep: {name: 'react-native-foo'},
+    });
+    expect(() => run(app)).toThrow(SpmNameCollisionError);
+    expect(() => run(app)).toThrow(
+      /the 'spm.modules' entry 'ReactNativeFoo' is already the name of another autolinked target/,
+    );
+  });
+});
+
 // ---------------------------------------------------------------------------
 // main() — plugin flavoredFrameworks sidecar
 //
diff --git a/packages/react-native/scripts/spm/expand-spm-dependencies.js b/packages/react-native/scripts/spm/expand-spm-dependencies.js
index dead1f9bb11..4bee4044797 100644
--- a/packages/react-native/scripts/spm/expand-spm-dependencies.js
+++ b/packages/react-native/scripts/spm/expand-spm-dependencies.js
@@ -71,6 +71,7 @@ class SpmNameCollisionError extends Error {
 
 // The charset `spm.name` must satisfy — permissive on purpose, since it has to
 // admit header-dir style (lowercase with hyphens) as well as Swift identifiers.
+// Shared with the app's own `spm.modules` names.
 function isValidSwiftName(name /*: unknown */) /*: boolean */ {
   return typeof name === 'string' && /^[A-Za-z_][A-Za-z0-9_-]*$/.test(name);
 }
diff --git a/packages/react-native/scripts/spm/generate-spm-autolinking.js b/packages/react-native/scripts/spm/generate-spm-autolinking.js
index 3cdee1d2645..4d21ebeb0fc 100644
--- a/packages/react-native/scripts/spm/generate-spm-autolinking.js
+++ b/packages/react-native/scripts/spm/generate-spm-autolinking.js
@@ -59,9 +59,12 @@
 
 const {discoverPlugins, invokePlugins} = require('./autolinking-plugins');
 const {
+  SpmNameCollisionError,
+  assertSwiftNameNotReserved,
   defaultReadConfig,
   defaultResolveDep,
   expandSpmDependencies,
+  isValidSwiftName,
 } = require('./expand-spm-dependencies');
 const {readPodspec} = require('./read-podspec');
 const {
@@ -265,6 +268,41 @@ function readSpmModulesFromConfig(
   }
 }
 
+/**
+ * Validates one app-local `spm.modules` name against the same rules a library's
+ * `spm.name` gets: a usable Swift identifier, not a name React Native reserves,
+ * and not one already taken by another module or an autolinked dep.
+ * `taken` maps lower-cased name → the name as written.
+ */
+function assertSpmModuleName(
+  name /*: unknown */,
+  taken /*: Map<string, string> */,
+) /*: void */ {
+  const remedy =
+    "Rename it in this app's react-native.config.js 'spm.modules'.";
+  if (typeof name !== 'string' || !isValidSwiftName(name)) {
+    throw new Error(
+      `react-native autolinking: invalid 'spm.modules' name ${JSON.stringify(name) ?? 'undefined'}: must start with a letter or underscore and contain only letters, digits, underscores, or hyphens.`,
+    );
+  }
+  const moduleName = name;
+  assertSwiftNameNotReserved(moduleName, {
+    label: `the 'spm.modules' entry '${moduleName}'`,
+    remedy,
+    extraReservedNames: reservedNamesForRun(),
+  });
+  const clash = taken.get(moduleName.toLowerCase());
+  if (clash != null) {
+    throw new SpmNameCollisionError(
+      `react-native autolinking: SPM Swift name collision: the 'spm.modules' entry '${moduleName}' ` +
+        (clash === moduleName
+          ? `is already the name of another autolinked target.`
+          : `differs from the existing target '${clash}' only in case, which collides on case-insensitive filesystems.`) +
+        ` ${remedy}`,
+    );
+  }
+}
+
 /**
  * Reads the app's `spm.denyPlugins` — npm names of autolinking plugins to
  * skip. The escape hatch for the transitive plugin discovery (an app opts a
@@ -1347,7 +1385,15 @@ function main(argv /*:: ?: Array<string> */) /*: void */ {
   // the globs now relative to its dir and attach the file list to the target
   // so the emission loop below renders `sources: [...]` literally.
   const configModules = readSpmModulesFromConfig(appRoot);
+  // Module names land in the manifest exactly as written, so they get the same
+  // checks a dep's Swift name gets. Seeded with the dep target names already
+  // emitted so a module can't shadow an autolinked library either.
+  const takenSwiftNames /*: Map<string, string> */ = new Map(
+    entries.map(entry => [entry.target.name.toLowerCase(), entry.target.name]),
+  );
   for (const mod of configModules) {
+    assertSpmModuleName(mod.name, takenSwiftNames);
+    takenSwiftNames.set(mod.name.toLowerCase(), mod.name);
     const absPath = path.resolve(appRoot, mod.path);
     const relPath = path.relative(outputDir, absPath);
     const userSources =