diff --git a/.changeset/odd-tools-work.md b/.changeset/odd-tools-work.md
new file mode 100644
index 0000000000..1ecfdba7e8
--- /dev/null
+++ b/.changeset/odd-tools-work.md
@@ -0,0 +1,5 @@
+---
+"react-router": patch
+---
+
+Remove `Navigator` declaration for `navigator.connection.saveData` to avoid messing with any other types beyond `saveData` in userland
diff --git a/packages/react-router/lib/dom/ssr/fog-of-war.ts b/packages/react-router/lib/dom/ssr/fog-of-war.ts
index 741c280792..87a3ff3246 100644
--- a/packages/react-router/lib/dom/ssr/fog-of-war.ts
+++ b/packages/react-router/lib/dom/ssr/fog-of-war.ts
@@ -9,12 +9,6 @@ import type { EntryRoute } from "./routes";
 import { createClientRoutes } from "./routes";
 import type { ServerBuild } from "../../server-runtime/build";
 
-declare global {
-  interface Navigator {
-    connection?: { saveData: boolean };
-  }
-}
-
 // Currently rendered links that may need prefetching
 const nextPaths = new Set<string>();
 
@@ -115,7 +109,8 @@ export function useFogOFWarDiscovery(
     // Don't prefetch if not enabled or if the user has `saveData` enabled
     if (
       !isFogOfWarEnabled(routeDiscovery, ssr) ||
-      navigator.connection?.saveData === true
+      // @ts-expect-error - TS doesn't know about this yet
+      window.navigator?.connection?.saveData === true
     ) {
       return;
     }