diff --git a/.changeset/real-rules-compare.md b/.changeset/real-rules-compare.md
new file mode 100644
index 0000000000..0ff7047f04
--- /dev/null
+++ b/.changeset/real-rules-compare.md
@@ -0,0 +1,5 @@
+---
+"react-router": patch
+---
+
+Fix `TypeError` if you throw from `patchRoutesOnNavigation` when no partial matches exist
diff --git a/packages/react-router/__tests__/router/lazy-discovery-test.ts b/packages/react-router/__tests__/router/lazy-discovery-test.ts
index 856301b611..3700f3886f 100644
--- a/packages/react-router/__tests__/router/lazy-discovery-test.ts
+++ b/packages/react-router/__tests__/router/lazy-discovery-test.ts
@@ -2103,6 +2103,91 @@ describe("Lazy Route Discovery (Fog of War)", () => {
       expect(router.state.matches.map((m) => m.route.id)).toEqual(["a", "b"]);
     });
 
+    it("handles errors thrown from patchRoutesOnNavigation() when there are no partial matches (GET navigation)", async () => {
+      router = createRouter({
+        history: createMemoryHistory(),
+        routes: [
+          {
+            id: "a",
+            path: "a",
+          },
+        ],
+        async patchRoutesOnNavigation({ patch }) {
+          await tick();
+          throw new Error("broke!");
+        },
+      });
+
+      await router.navigate("/b");
+      expect(router.state).toMatchObject({
+        // A bit odd but this is a result of our best attempt to display some form
+        // of error UI to the user - follows the same logic we use on 404s
+        matches: [
+          {
+            params: {},
+            pathname: "",
+            pathnameBase: "",
+            route: {
+              children: undefined,
+              hasErrorBoundary: false,
+              id: "a",
+              path: "a",
+            },
+          },
+        ],
+        location: { pathname: "/b" },
+        actionData: null,
+        loaderData: {},
+        errors: {
+          a: new Error("broke!"),
+        },
+      });
+    });
+
+    it("handles errors thrown from patchRoutesOnNavigation() when there are no partial matches (POST navigation)", async () => {
+      router = createRouter({
+        history: createMemoryHistory(),
+        routes: [
+          {
+            id: "a",
+            path: "a",
+          },
+        ],
+        async patchRoutesOnNavigation({ patch }) {
+          await tick();
+          throw new Error("broke!");
+        },
+      });
+
+      await router.navigate("/b", {
+        formMethod: "POST",
+        formData: createFormData({}),
+      });
+      expect(router.state).toMatchObject({
+        // A bit odd but this is a result of our best attempt to display some form
+        // of error UI to the user - follows the same logic we use on 404s
+        matches: [
+          {
+            params: {},
+            pathname: "",
+            pathnameBase: "",
+            route: {
+              children: undefined,
+              hasErrorBoundary: false,
+              id: "a",
+              path: "a",
+            },
+          },
+        ],
+        location: { pathname: "/b" },
+        actionData: null,
+        loaderData: {},
+        errors: {
+          a: new Error("broke!"),
+        },
+      });
+    });
+
     it("bubbles errors thrown from patchRoutesOnNavigation() during hydration", async () => {
       router = createRouter({
         history: createMemoryHistory({
diff --git a/packages/react-router/lib/router/router.ts b/packages/react-router/lib/router/router.ts
index c9e9809c96..dc85b2e2b1 100644
--- a/packages/react-router/lib/router/router.ts
+++ b/packages/react-router/lib/router/router.ts
@@ -1802,6 +1802,20 @@ export function createRouter(init: RouterInit): Router {
       if (discoverResult.type === "aborted") {
         return { shortCircuited: true };
       } else if (discoverResult.type === "error") {
+        if (discoverResult.partialMatches.length === 0) {
+          let { matches, route } = getShortCircuitMatches(dataRoutes);
+          return {
+            matches,
+            pendingActionResult: [
+              route.id,
+              {
+                type: ResultType.error,
+                error: discoverResult.error,
+              },
+            ],
+          };
+        }
+
         let boundaryId = findNearestBoundary(discoverResult.partialMatches)
           .route.id;
         return {
@@ -1996,6 +2010,17 @@ export function createRouter(init: RouterInit): Router {
       if (discoverResult.type === "aborted") {
         return { shortCircuited: true };
       } else if (discoverResult.type === "error") {
+        if (discoverResult.partialMatches.length === 0) {
+          let { matches, route } = getShortCircuitMatches(dataRoutes);
+          return {
+            matches,
+            loaderData: {},
+            errors: {
+              [route.id]: discoverResult.error,
+            },
+          };
+        }
+
         let boundaryId = findNearestBoundary(discoverResult.partialMatches)
           .route.id;
         return {