diff --git a/packages/browser-utils/src/instrumentation/location.ts b/packages/browser-utils/src/instrumentation/location.ts
index 7b6dfc5243a0..5e62a777129e 100644
--- a/packages/browser-utils/src/instrumentation/location.ts
+++ b/packages/browser-utils/src/instrumentation/location.ts
@@ -6,6 +6,8 @@ import { WINDOW } from '../types';
  *
  * @return the absolute URL when handed a relative URL path, by
  * combining the current `window.location.origin` with param urlOrPath.
+ * A path starting with `//` is treated as a path on the current origin,
+ * not as a protocol-relative URL.
  *
  * If param urlOrPath is already a full or an invalid URL,
  * or URL determination fails, the original param urlOrPath is returned unchanged.
@@ -13,7 +15,10 @@ import { WINDOW } from '../types';
  */
 export function getAbsoluteUrl(urlOrPath: string): string {
   try {
-    const url = new URL(urlOrPath, WINDOW.location.origin);
+    const origin = WINDOW.location.origin;
+    // Callers pass untyped router arguments, which `new URL` used to stringify for us.
+    const path = String(urlOrPath);
+    const url = path.startsWith('//') ? new URL(`${origin}${path}`) : new URL(path, origin);
     return url.toString();
   } catch {
     // fallback, just do nothing
diff --git a/packages/browser-utils/test/instrumentation/location.test.ts b/packages/browser-utils/test/instrumentation/location.test.ts
index c67820d33fff..8d28b55d7a3b 100644
--- a/packages/browser-utils/test/instrumentation/location.test.ts
+++ b/packages/browser-utils/test/instrumentation/location.test.ts
@@ -24,4 +24,11 @@ describe('getAbsoluteUrl', () => {
   it('returns fragments', () => {
     expect(getAbsoluteUrl('/foo#bar')).toBe('https://sentry.io/foo#bar');
   });
+
+  it.each([
+    ['//foo/bar', 'https://sentry.io//foo/bar'],
+    ['//foo/bar?x=1#h', 'https://sentry.io//foo/bar?x=1#h'],
+  ])('keeps the current origin for a path starting with `//` (%s)', (path, expected) => {
+    expect(getAbsoluteUrl(path)).toBe(expected);
+  });
 });
diff --git a/packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts b/packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts
index f2f933bc11bf..5a20f7b68b76 100644
--- a/packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts
+++ b/packages/nextjs/src/client/routing/appRouterRoutingInstrumentation.ts
@@ -26,10 +26,20 @@ import {
 } from '@sentry/conventions/attributes';
 import { NAVIGATION } from '@sentry/conventions/op';
 
+/**
+ * Unlike `getAbsoluteUrl`, keeps a `//host/path` target protocol-relative: Next.js treats such an
+ * href as an external URL and navigates to that host.
+ */
+function getNavigationTargetUrl(href: string): string {
+  // `router.push()` arguments reach this untyped, so a non-string must not throw here.
+  const isProtocolRelative = typeof href === 'string' && href.startsWith('//');
+  return getAbsoluteUrl(isProtocolRelative ? `${WINDOW.location.protocol}${href}` : href);
+}
+
 function setNavigationSpanUrlAttributes(span: Span, urlPath: string, urlOrPath: string): void {
   span.setAttributes({
     [URL_PATH]: urlPath,
-    [URL_FULL]: filterCollectedUrl(getAbsoluteUrl(urlOrPath)),
+    [URL_FULL]: filterCollectedUrl(getNavigationTargetUrl(urlOrPath)),
   });
 }
 
@@ -170,7 +180,7 @@ export function appRouterInstrumentNavigation(client: Client): void {
             [URL_TEMPLATE]: parameterizedPathname,
           },
         },
-        { url: getAbsoluteUrl(normalizedHref) },
+        { url: getNavigationTargetUrl(normalizedHref) },
       );
     }
   };
@@ -306,7 +316,7 @@ function patchRouter(client: Client, router: NextRouter, currentNavigationSpanRe
                 [URL_TEMPLATE]: parameterizedPathname,
               },
             },
-            { url: getAbsoluteUrl(normalizedHref) },
+            { url: getNavigationTargetUrl(normalizedHref) },
           );
 
           return target.apply(thisArg, argArray);
diff --git a/packages/nextjs/test/client/appRouterRoutingInstrumentation.test.ts b/packages/nextjs/test/client/appRouterRoutingInstrumentation.test.ts
index 25ecbfdd3f80..4d94c5dd2cdc 100644
--- a/packages/nextjs/test/client/appRouterRoutingInstrumentation.test.ts
+++ b/packages/nextjs/test/client/appRouterRoutingInstrumentation.test.ts
@@ -196,6 +196,26 @@ describe('appRouterInstrumentNavigation (router-patch mode)', () => {
       expect(core.spanToJSON(pushSpan!).end_timestamp).toBeDefined();
     });
 
+    it('records a protocol-relative `router.push()` target as an external URL', async () => {
+      const { core, router } = await setup(traceLifecycle);
+
+      router.push('//cdn.example.com/x');
+
+      expect(core.spanToJSON(core.getActiveSpan()!).attributes).toEqual(
+        expect.objectContaining({ [URL_FULL]: 'http://cdn.example.com/x' }),
+      );
+    });
+
+    it('records a protocol-relative transition-start-hook target as an external URL', async () => {
+      const { core, instrumentation } = await setup(traceLifecycle);
+
+      instrumentation.captureRouterTransitionStart('//cdn.example.com/x', 'push');
+
+      expect(core.spanToJSON(core.getActiveSpan()!).attributes).toEqual(
+        expect.objectContaining({ [URL_FULL]: 'http://cdn.example.com/x' }),
+      );
+    });
+
     it('tags a popstate without a preceding router call with `browser.popstate`', async () => {
       const { core } = await setup(traceLifecycle);
 
@@ -260,6 +280,16 @@ describe('appRouterInstrumentNavigation with basePath', () => {
     );
   });
 
+  it('records a `//` target as a path under basePath, like Next.js does', async () => {
+    const { core, router } = await setup('static');
+
+    router.push('//cdn.example.com/x');
+
+    expect(core.spanToJSON(core.getActiveSpan()!).attributes).toEqual(
+      expect.objectContaining({ [URL_FULL]: 'http://localhost:3000/my-app//cdn.example.com/x' }),
+    );
+  });
+
   it.each([
     ['a root-relative path without basePath', '/navigation/42/router-push'],
     ['a root-relative path with basePath', '/my-app/navigation/42/router-push'],