diff --git a/.changeset/gentle-hoops-shave.md b/.changeset/gentle-hoops-shave.md
new file mode 100644
index 00000000000..e2e8c12e6e4
--- /dev/null
+++ b/.changeset/gentle-hoops-shave.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/router-core': patch
+---
+
+allow Temporal types in serializable data
diff --git a/e2e/react-start/serialization-adapters/package.json b/e2e/react-start/serialization-adapters/package.json
index 0e0d157733c..27633b4e50d 100644
--- a/e2e/react-start/serialization-adapters/package.json
+++ b/e2e/react-start/serialization-adapters/package.json
@@ -17,6 +17,7 @@
     "@tanstack/react-start": "workspace:^",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
+    "temporal-polyfill": "^1.0.4",
     "zod": "^4.4.3"
   },
   "devDependencies": {
diff --git a/e2e/react-start/serialization-adapters/src/client.tsx b/e2e/react-start/serialization-adapters/src/client.tsx
new file mode 100644
index 00000000000..4ba538c19b8
--- /dev/null
+++ b/e2e/react-start/serialization-adapters/src/client.tsx
@@ -0,0 +1,15 @@
+import { StrictMode, startTransition } from 'react'
+import { hydrateRoot } from 'react-dom/client'
+import { StartClient } from '@tanstack/react-start/client'
+import { install as installTemporalPolyfill } from 'temporal-polyfill/shim'
+
+installTemporalPolyfill()
+
+startTransition(() => {
+  hydrateRoot(
+    document,
+    <StrictMode>
+      <StartClient />
+    </StrictMode>,
+  )
+})
diff --git a/e2e/react-start/serialization-adapters/src/routeTree.gen.ts b/e2e/react-start/serialization-adapters/src/routeTree.gen.ts
index 1b21d4200b7..bb6c30b459f 100644
--- a/e2e/react-start/serialization-adapters/src/routeTree.gen.ts
+++ b/e2e/react-start/serialization-adapters/src/routeTree.gen.ts
@@ -13,9 +13,11 @@ import { Route as IndexRouteImport } from './routes/index'
 import { Route as ServerFunctionCustomErrorRouteImport } from './routes/server-function/custom-error'
 import { Route as ServerFunctionLateRawStreamRouteImport } from './routes/server-function/late-raw-stream'
 import { Route as ServerFunctionNestedRouteImport } from './routes/server-function/nested'
+import { Route as ServerFunctionTemporalRouteImport } from './routes/server-function/temporal'
 import { Route as SsrDataOnlyRouteImport } from './routes/ssr/data-only'
 import { Route as SsrNestedRouteImport } from './routes/ssr/nested'
 import { Route as SsrStreamRouteImport } from './routes/ssr/stream'
+import { Route as SsrTemporalRouteImport } from './routes/ssr/temporal'
 
 const IndexRoute = IndexRouteImport.update({
   id: '/',
@@ -39,6 +41,11 @@ const ServerFunctionNestedRoute = ServerFunctionNestedRouteImport.update({
   path: '/server-function/nested',
   getParentRoute: () => rootRouteImport,
 } as any)
+const ServerFunctionTemporalRoute = ServerFunctionTemporalRouteImport.update({
+  id: '/server-function/temporal',
+  path: '/server-function/temporal',
+  getParentRoute: () => rootRouteImport,
+} as any)
 const SsrDataOnlyRoute = SsrDataOnlyRouteImport.update({
   id: '/ssr/data-only',
   path: '/ssr/data-only',
@@ -54,24 +61,33 @@ const SsrStreamRoute = SsrStreamRouteImport.update({
   path: '/ssr/stream',
   getParentRoute: () => rootRouteImport,
 } as any)
+const SsrTemporalRoute = SsrTemporalRouteImport.update({
+  id: '/ssr/temporal',
+  path: '/ssr/temporal',
+  getParentRoute: () => rootRouteImport,
+} as any)
 
 export interface FileRoutesByFullPath {
   '/': typeof IndexRoute
   '/server-function/custom-error': typeof ServerFunctionCustomErrorRoute
   '/server-function/late-raw-stream': typeof ServerFunctionLateRawStreamRoute
   '/server-function/nested': typeof ServerFunctionNestedRoute
+  '/server-function/temporal': typeof ServerFunctionTemporalRoute
   '/ssr/data-only': typeof SsrDataOnlyRoute
   '/ssr/nested': typeof SsrNestedRoute
   '/ssr/stream': typeof SsrStreamRoute
+  '/ssr/temporal': typeof SsrTemporalRoute
 }
 export interface FileRoutesByTo {
   '/': typeof IndexRoute
   '/server-function/custom-error': typeof ServerFunctionCustomErrorRoute
   '/server-function/late-raw-stream': typeof ServerFunctionLateRawStreamRoute
   '/server-function/nested': typeof ServerFunctionNestedRoute
+  '/server-function/temporal': typeof ServerFunctionTemporalRoute
   '/ssr/data-only': typeof SsrDataOnlyRoute
   '/ssr/nested': typeof SsrNestedRoute
   '/ssr/stream': typeof SsrStreamRoute
+  '/ssr/temporal': typeof SsrTemporalRoute
 }
 export interface FileRoutesById {
   __root__: typeof rootRouteImport
@@ -79,9 +95,11 @@ export interface FileRoutesById {
   '/server-function/custom-error': typeof ServerFunctionCustomErrorRoute
   '/server-function/late-raw-stream': typeof ServerFunctionLateRawStreamRoute
   '/server-function/nested': typeof ServerFunctionNestedRoute
+  '/server-function/temporal': typeof ServerFunctionTemporalRoute
   '/ssr/data-only': typeof SsrDataOnlyRoute
   '/ssr/nested': typeof SsrNestedRoute
   '/ssr/stream': typeof SsrStreamRoute
+  '/ssr/temporal': typeof SsrTemporalRoute
 }
 export interface FileRouteTypes {
   fileRoutesByFullPath: FileRoutesByFullPath
@@ -90,27 +108,33 @@ export interface FileRouteTypes {
     | '/server-function/custom-error'
     | '/server-function/late-raw-stream'
     | '/server-function/nested'
+    | '/server-function/temporal'
     | '/ssr/data-only'
     | '/ssr/nested'
     | '/ssr/stream'
+    | '/ssr/temporal'
   fileRoutesByTo: FileRoutesByTo
   to:
     | '/'
     | '/server-function/custom-error'
     | '/server-function/late-raw-stream'
     | '/server-function/nested'
+    | '/server-function/temporal'
     | '/ssr/data-only'
     | '/ssr/nested'
     | '/ssr/stream'
+    | '/ssr/temporal'
   id:
     | '__root__'
     | '/'
     | '/server-function/custom-error'
     | '/server-function/late-raw-stream'
     | '/server-function/nested'
+    | '/server-function/temporal'
     | '/ssr/data-only'
     | '/ssr/nested'
     | '/ssr/stream'
+    | '/ssr/temporal'
   fileRoutesById: FileRoutesById
 }
 export interface RootRouteChildren {
@@ -118,9 +142,11 @@ export interface RootRouteChildren {
   ServerFunctionCustomErrorRoute: typeof ServerFunctionCustomErrorRoute
   ServerFunctionLateRawStreamRoute: typeof ServerFunctionLateRawStreamRoute
   ServerFunctionNestedRoute: typeof ServerFunctionNestedRoute
+  ServerFunctionTemporalRoute: typeof ServerFunctionTemporalRoute
   SsrDataOnlyRoute: typeof SsrDataOnlyRoute
   SsrNestedRoute: typeof SsrNestedRoute
   SsrStreamRoute: typeof SsrStreamRoute
+  SsrTemporalRoute: typeof SsrTemporalRoute
 }
 
 declare module '@tanstack/react-router' {
@@ -153,6 +179,13 @@ declare module '@tanstack/react-router' {
       preLoaderRoute: typeof ServerFunctionNestedRouteImport
       parentRoute: typeof rootRouteImport
     }
+    '/server-function/temporal': {
+      id: '/server-function/temporal'
+      path: '/server-function/temporal'
+      fullPath: '/server-function/temporal'
+      preLoaderRoute: typeof ServerFunctionTemporalRouteImport
+      parentRoute: typeof rootRouteImport
+    }
     '/ssr/data-only': {
       id: '/ssr/data-only'
       path: '/ssr/data-only'
@@ -174,6 +207,13 @@ declare module '@tanstack/react-router' {
       preLoaderRoute: typeof SsrStreamRouteImport
       parentRoute: typeof rootRouteImport
     }
+    '/ssr/temporal': {
+      id: '/ssr/temporal'
+      path: '/ssr/temporal'
+      fullPath: '/ssr/temporal'
+      preLoaderRoute: typeof SsrTemporalRouteImport
+      parentRoute: typeof rootRouteImport
+    }
   }
 }
 
@@ -182,9 +222,11 @@ const rootRouteChildren: RootRouteChildren = {
   ServerFunctionCustomErrorRoute: ServerFunctionCustomErrorRoute,
   ServerFunctionLateRawStreamRoute: ServerFunctionLateRawStreamRoute,
   ServerFunctionNestedRoute: ServerFunctionNestedRoute,
+  ServerFunctionTemporalRoute: ServerFunctionTemporalRoute,
   SsrDataOnlyRoute: SsrDataOnlyRoute,
   SsrNestedRoute: SsrNestedRoute,
   SsrStreamRoute: SsrStreamRoute,
+  SsrTemporalRoute: SsrTemporalRoute,
 }
 export const routeTree = rootRouteImport
   ._addFileChildren(rootRouteChildren)
diff --git a/e2e/react-start/serialization-adapters/src/routes/index.tsx b/e2e/react-start/serialization-adapters/src/routes/index.tsx
index e39d32cd639..f4b8b98c5b6 100644
--- a/e2e/react-start/serialization-adapters/src/routes/index.tsx
+++ b/e2e/react-start/serialization-adapters/src/routes/index.tsx
@@ -32,6 +32,14 @@ function Home() {
         >
           Nested Classes
         </Link>
+        <br />
+        <Link
+          data-testid="ssr-temporal-link"
+          to="/ssr/temporal"
+          reloadDocument={true}
+        >
+          Temporal
+        </Link>
       </div>
       <div>
         <h2>Server Functions</h2>
@@ -50,6 +58,14 @@ function Home() {
         >
           Nested Classes returned from Server Function
         </Link>
+        <br />
+        <Link
+          data-testid="server-functions-temporal-link"
+          to="/server-function/temporal"
+          reloadDocument={true}
+        >
+          Temporal returned from Server Function
+        </Link>
       </div>
     </>
   )
diff --git a/e2e/react-start/serialization-adapters/src/routes/server-function/temporal.tsx b/e2e/react-start/serialization-adapters/src/routes/server-function/temporal.tsx
new file mode 100644
index 00000000000..ac07bb6e533
--- /dev/null
+++ b/e2e/react-start/serialization-adapters/src/routes/server-function/temporal.tsx
@@ -0,0 +1,34 @@
+import { createFileRoute } from '@tanstack/react-router'
+import { createServerFn } from '@tanstack/react-start'
+import { useState } from 'react'
+import type { TemporalData } from '~/temporal'
+import { RenderTemporalData, makeTemporalData } from '~/temporal'
+
+const temporalFn = createServerFn().handler(() => {
+  return makeTemporalData()
+})
+
+export const Route = createFileRoute('/server-function/temporal')({
+  component: RouteComponent,
+})
+
+function RouteComponent() {
+  const [temporalResponse, setTemporalResponse] = useState<TemporalData>()
+
+  return (
+    <div>
+      <button
+        data-testid="server-function-trigger"
+        onClick={() => temporalFn().then(setTemporalResponse)}
+      >
+        trigger
+      </button>
+
+      {temporalResponse ? (
+        <RenderTemporalData id="server-fn" data={temporalResponse} />
+      ) : (
+        <div data-testid="waiting-for-response">waiting for response...</div>
+      )}
+    </div>
+  )
+}
diff --git a/e2e/react-start/serialization-adapters/src/routes/ssr/temporal.tsx b/e2e/react-start/serialization-adapters/src/routes/ssr/temporal.tsx
new file mode 100644
index 00000000000..683bb3e67df
--- /dev/null
+++ b/e2e/react-start/serialization-adapters/src/routes/ssr/temporal.tsx
@@ -0,0 +1,11 @@
+import { createFileRoute } from '@tanstack/react-router'
+import { RenderTemporalData, makeTemporalData } from '~/temporal'
+
+export const Route = createFileRoute('/ssr/temporal')({
+  loader: () => makeTemporalData(),
+  component: () => {
+    const loaderData = Route.useLoaderData()
+
+    return <RenderTemporalData id="loader" data={loaderData} />
+  },
+})
diff --git a/e2e/react-start/serialization-adapters/src/server.ts b/e2e/react-start/serialization-adapters/src/server.ts
new file mode 100644
index 00000000000..1777d7ee92d
--- /dev/null
+++ b/e2e/react-start/serialization-adapters/src/server.ts
@@ -0,0 +1,10 @@
+import handler from '@tanstack/react-start/server-entry'
+import { install as installTemporalPolyfill } from 'temporal-polyfill/shim'
+
+installTemporalPolyfill()
+
+export default {
+  fetch(request: Request) {
+    return handler.fetch(request)
+  },
+}
diff --git a/e2e/react-start/serialization-adapters/src/temporal-global.d.ts b/e2e/react-start/serialization-adapters/src/temporal-global.d.ts
new file mode 100644
index 00000000000..a29f92fe362
--- /dev/null
+++ b/e2e/react-start/serialization-adapters/src/temporal-global.d.ts
@@ -0,0 +1 @@
+import 'temporal-polyfill/types/global'
diff --git a/e2e/react-start/serialization-adapters/src/temporal.tsx b/e2e/react-start/serialization-adapters/src/temporal.tsx
new file mode 100644
index 00000000000..2885cda72c3
--- /dev/null
+++ b/e2e/react-start/serialization-adapters/src/temporal.tsx
@@ -0,0 +1,56 @@
+export const temporalTypeNames = [
+  'Instant',
+  'Duration',
+  'PlainDate',
+  'PlainDateTime',
+  'PlainMonthDay',
+  'PlainTime',
+  'PlainYearMonth',
+  'ZonedDateTime',
+] as const
+
+export function makeTemporalData() {
+  return {
+    Instant: Temporal.Instant.from('2024-03-05T06:07:08.9Z'),
+    Duration: Temporal.Duration.from('P1Y2M3DT4H5M6.7S'),
+    PlainDate: Temporal.PlainDate.from('2024-03-05'),
+    PlainDateTime: Temporal.PlainDateTime.from('2024-03-05T06:07:08.9'),
+    PlainMonthDay: Temporal.PlainMonthDay.from('03-05'),
+    PlainTime: Temporal.PlainTime.from('06:07:08.9'),
+    PlainYearMonth: Temporal.PlainYearMonth.from('2024-03'),
+    ZonedDateTime: Temporal.ZonedDateTime.from(
+      '2024-03-05T06:07:08.9+01:00[Europe/Berlin]',
+    ),
+  }
+}
+
+export type TemporalData = ReturnType<typeof makeTemporalData>
+
+function formatTemporal(value: unknown) {
+  return `${Object.prototype.toString.call(value)} ${String(value)}`
+}
+
+export function RenderTemporalData({
+  id,
+  data,
+}: {
+  id: string
+  data: TemporalData
+}) {
+  const localData = makeTemporalData()
+  return (
+    <div data-testid={`${id}-container`}>
+      {temporalTypeNames.map((name) => (
+        <div key={name}>
+          <h4>{name}</h4>
+          <div data-testid={`${id}-${name}-expected`}>
+            {formatTemporal(localData[name])}
+          </div>
+          <div data-testid={`${id}-${name}-actual`}>
+            {formatTemporal(data[name])}
+          </div>
+        </div>
+      ))}
+    </div>
+  )
+}
diff --git a/e2e/react-start/serialization-adapters/tests/app.spec.ts b/e2e/react-start/serialization-adapters/tests/app.spec.ts
index 26f70e81b07..ebec811e9db 100644
--- a/e2e/react-start/serialization-adapters/tests/app.spec.ts
+++ b/e2e/react-start/serialization-adapters/tests/app.spec.ts
@@ -39,6 +39,29 @@ async function checkNestedData(page: Page) {
     expectedWhisper!,
   )
 }
+
+const temporalTypeNames = [
+  'Instant',
+  'Duration',
+  'PlainDate',
+  'PlainDateTime',
+  'PlainMonthDay',
+  'PlainTime',
+  'PlainYearMonth',
+  'ZonedDateTime',
+] as const
+
+async function checkTemporalData(page: Page, id: string) {
+  for (const name of temporalTypeNames) {
+    const expected = await page
+      .getByTestId(`${id}-${name}-expected`)
+      .textContent()
+    expect(expected).not.toBeNull()
+    expect(expected).toContain(`[object Temporal.${name}]`)
+    await expect(page.getByTestId(`${id}-${name}-actual`)).toHaveText(expected!)
+  }
+}
+
 test.use({
   whitelistErrors: [
     'Failed to load resource: the server responded with a status of 499',
@@ -74,6 +97,13 @@ test.describe('SSR serialization adapters', () => {
 
     await checkNestedData(page)
   })
+
+  test('temporal', async ({ page }) => {
+    await page.goto('/ssr/temporal')
+    await awaitPageLoaded(page)
+
+    await checkTemporalData(page, 'loader')
+  })
 })
 
 test.describe('server functions serialization adapters', () => {
@@ -109,6 +139,18 @@ test.describe('server functions serialization adapters', () => {
     await page.getByTestId('server-function-trigger').click()
     await checkNestedData(page)
   })
+
+  test('temporal', async ({ page }) => {
+    await page.goto('/server-function/temporal')
+    await awaitPageLoaded(page)
+
+    await expect(page.getByTestId('waiting-for-response')).toContainText(
+      'waiting for response...',
+    )
+
+    await page.getByTestId('server-function-trigger').click()
+    await checkTemporalData(page, 'server-fn')
+  })
 })
 
 test.describe('late RawStream serialization', () => {
diff --git a/packages/router-core/src/ssr/serializer/transformer.ts b/packages/router-core/src/ssr/serializer/transformer.ts
index 6eeed9b6e66..f300a8aa306 100644
--- a/packages/router-core/src/ssr/serializer/transformer.ts
+++ b/packages/router-core/src/ssr/serializer/transformer.ts
@@ -15,6 +15,20 @@ export type TSR_SERIALIZABLE = typeof TSR_SERIALIZABLE
 
 export type TsrSerializable = { [TSR_SERIALIZABLE]: true }
 
+// Resolve `Temporal` from `globalThis` so it degrades to `never`, not `any`,
+// for consumers whose `lib` predates or omits `ESNext.Temporal`.
+type TemporalNamespace = typeof globalThis extends { Temporal: infer TTemporal }
+  ? TTemporal
+  : Record<never, never>
+
+type TemporalInstance<TKey extends PropertyKey> =
+  TemporalNamespace extends Record<
+    TKey,
+    abstract new (...args: any) => infer TInstance
+  >
+    ? TInstance
+    : never
+
 export interface DefaultSerializable {
   number: number
   string: string
@@ -26,6 +40,14 @@ export interface DefaultSerializable {
   Uint8Array: Uint8Array
   RawStream: RawStream
   TsrSerializable: TsrSerializable
+  TemporalInstant: TemporalInstance<'Instant'>
+  TemporalDuration: TemporalInstance<'Duration'>
+  TemporalPlainDate: TemporalInstance<'PlainDate'>
+  TemporalPlainDateTime: TemporalInstance<'PlainDateTime'>
+  TemporalPlainMonthDay: TemporalInstance<'PlainMonthDay'>
+  TemporalPlainTime: TemporalInstance<'PlainTime'>
+  TemporalPlainYearMonth: TemporalInstance<'PlainYearMonth'>
+  TemporalZonedDateTime: TemporalInstance<'ZonedDateTime'>
   void: void
 }
 
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index b5f19618d3f..724de523a2d 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -3308,6 +3308,9 @@ importers:
       react-dom:
         specifier: ^19.2.3
         version: 19.2.3(react@19.2.3)
+      temporal-polyfill:
+        specifier: ^1.0.4
+        version: 1.0.4
       zod:
         specifier: ^4.4.3
         version: 4.4.3
@@ -27575,6 +27578,15 @@ packages:
   teex@1.0.1:
     resolution: {integrity: sha512-eYE6iEI62Ni1H8oIa7KlDU6uQBtqr4Eajni3wX7rpfXD8ysFx8z0+dri+KWEPWpBsxXfxu58x/0jvTVT1ekOSg==}
 
+  temporal-polyfill@1.0.4:
+    resolution: {integrity: sha512-MLEU0qOD2uXlz24oINNtdLZQl8RgmMxSnRtKEGZGGetTJjlRwQJjk+VsJ4EREaUoiaTb8NJOcUiKtoAiWn9EBg==}
+
+  temporal-spec@1.0.1:
+    resolution: {integrity: sha512-wxVoanmDeavXie1vu2JaQ3WIc3JZnWAOYFBsJyATaVsXsycKYUflGsyBmrRSnoCpZJpwPyr38VpgSUlQ8CbFxg==}
+
+  temporal-utils@1.0.2:
+    resolution: {integrity: sha512-1B8Dl4KzrOvsNUlpoWGno2VLQlxroLjDgc5NBjVC9ax9ymdo+ezfyvhyjEMx+IVfhINr6CIG2gcnlP95iRrybQ==}
+
   term-size@2.2.1:
     resolution: {integrity: sha512-wK0Ri4fOGjv/XPy8SBHZChl8CM7uMc5VML7SqiQ0zG7+J5Vr+RMQDoHa2CNT6KHUnTGIXH34UDMkPzAUyapBZg==}
     engines: {node: '>=8'}
@@ -42425,6 +42437,15 @@ snapshots:
     transitivePeerDependencies:
       - bare-abort-controller
 
+  temporal-polyfill@1.0.4:
+    dependencies:
+      temporal-spec: 1.0.1
+      temporal-utils: 1.0.2
+
+  temporal-spec@1.0.1: {}
+
+  temporal-utils@1.0.2: {}
+
   term-size@2.2.1: {}
 
   terser-webpack-plugin@5.3.11(@swc/core@1.15.33(@swc/helpers@0.5.23))(esbuild@0.27.4)(webpack@5.97.1):