diff --git a/.changeset/form-action-hash.md b/.changeset/form-action-hash.md
new file mode 100644
index 0000000000..36fe2e2907
--- /dev/null
+++ b/.changeset/form-action-hash.md
@@ -0,0 +1,5 @@
+---
+"react-router-dom": patch
+---
+
+Do not include hash in `useFormAction()` for unspecified actions since it cannot be determined on the server and causes hydration issues
diff --git a/packages/react-router-dom/__tests__/data-browser-router-test.tsx b/packages/react-router-dom/__tests__/data-browser-router-test.tsx
index 83828d986e..3ef5bc3ec2 100644
--- a/packages/react-router-dom/__tests__/data-browser-router-test.tsx
+++ b/packages/react-router-dom/__tests__/data-browser-router-test.tsx
@@ -2529,7 +2529,7 @@ function testDomRouter(
       }
 
       describe("static routes", () => {
-        it("includes search params + hash when no action is specified", async () => {
+        it("includes search params when no action is specified", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2545,11 +2545,11 @@ function testDomRouter(
           let { container } = render(<RouterProvider router={router} />);
 
           expect(container.querySelector("form")?.getAttribute("action")).toBe(
-            "/foo/bar?a=1#hash"
+            "/foo/bar?a=1"
           );
         });
 
-        it("does not include search params + hash when action='.'", async () => {
+        it("does not include search params when action='.'", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2567,7 +2567,7 @@ function testDomRouter(
           );
         });
 
-        it("does not include search params + hash when action=''", async () => {
+        it("does not include search params when action=''", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2587,7 +2587,7 @@ function testDomRouter(
       });
 
       describe("layout routes", () => {
-        it("includes search params + hash when no action is specified", async () => {
+        it("includes search params when no action is specified", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2605,11 +2605,11 @@ function testDomRouter(
           let { container } = render(<RouterProvider router={router} />);
 
           expect(container.querySelector("form")?.getAttribute("action")).toBe(
-            "/foo/bar?a=1#hash"
+            "/foo/bar?a=1"
           );
         });
 
-        it("does not include search params + hash when action='.'", async () => {
+        it("does not include search params when action='.'", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2631,7 +2631,7 @@ function testDomRouter(
           );
         });
 
-        it("does not include search params + hash when action=''", async () => {
+        it("does not include search params when action=''", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2655,7 +2655,7 @@ function testDomRouter(
       });
 
       describe("index routes", () => {
-        it("includes search params + hash when no action is specified", async () => {
+        it("includes search params when no action is specified", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2673,11 +2673,11 @@ function testDomRouter(
           let { container } = render(<RouterProvider router={router} />);
 
           expect(container.querySelector("form")?.getAttribute("action")).toBe(
-            "/foo/bar?index&a=1#hash"
+            "/foo/bar?index&a=1"
           );
         });
 
-        it("does not include search params + hash action='.'", async () => {
+        it("does not include search params action='.'", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2699,7 +2699,7 @@ function testDomRouter(
           );
         });
 
-        it("does not include search params + hash action=''", async () => {
+        it("does not include search params action=''", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2777,7 +2777,7 @@ function testDomRouter(
           let { container } = render(<RouterProvider router={router} />);
 
           expect(container.querySelector("form")?.getAttribute("action")).toBe(
-            "/foo/bar?index&a=1#hash"
+            "/foo/bar?index&a=1"
           );
         });
 
@@ -2816,7 +2816,7 @@ function testDomRouter(
       });
 
       describe("dynamic routes", () => {
-        it("includes search params + hash when no action is specified", async () => {
+        it("includes search params when no action is specified", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2832,11 +2832,11 @@ function testDomRouter(
           let { container } = render(<RouterProvider router={router} />);
 
           expect(container.querySelector("form")?.getAttribute("action")).toBe(
-            "/foo/bar?a=1#hash"
+            "/foo/bar?a=1"
           );
         });
 
-        it("does not include search params + hash action='.'", async () => {
+        it("does not include search params action='.'", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2856,7 +2856,7 @@ function testDomRouter(
           );
         });
 
-        it("does not include search params + hash when action=''", async () => {
+        it("does not include search params when action=''", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2878,7 +2878,7 @@ function testDomRouter(
       });
 
       describe("splat routes", () => {
-        it("includes search params + hash when no action is specified", async () => {
+        it("includes search params when no action is specified", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2894,11 +2894,11 @@ function testDomRouter(
           let { container } = render(<RouterProvider router={router} />);
 
           expect(container.querySelector("form")?.getAttribute("action")).toBe(
-            "/foo?a=1#hash"
+            "/foo?a=1"
           );
         });
 
-        it("does not include search params + hash when action='.'", async () => {
+        it("does not include search params when action='.'", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2918,7 +2918,7 @@ function testDomRouter(
           );
         });
 
-        it("does not include search params + hash when action=''", async () => {
+        it("does not include search params when action=''", async () => {
           let router = createTestRouter(
             createRoutesFromElements(
               <Route path="/">
@@ -2938,6 +2938,24 @@ function testDomRouter(
           );
         });
       });
+
+      it("allows user to specify search params and hash", async () => {
+        let router = createTestRouter(
+          createRoutesFromElements(
+            <Route path="/">
+              <Route path="foo">
+                <Route path="bar" element={<Form action=".?a=1#newhash" />} />
+              </Route>
+            </Route>
+          ),
+          { window: getWindow("/foo/bar?a=1#hash") }
+        );
+        let { container } = render(<RouterProvider router={router} />);
+
+        expect(container.querySelector("form")?.getAttribute("action")).toBe(
+          "/foo/bar?a=1#newhash"
+        );
+      });
     });
 
     describe('<Form action relative="path">', () => {
diff --git a/packages/react-router-dom/index.tsx b/packages/react-router-dom/index.tsx
index 5cf5763d29..283c5e364f 100644
--- a/packages/react-router-dom/index.tsx
+++ b/packages/react-router-dom/index.tsx
@@ -1157,17 +1157,15 @@ export function useFormAction(
   let path = { ...useResolvedPath(action ? action : ".", { relative }) };
 
   // Previously we set the default action to ".". The problem with this is that
-  // `useResolvedPath(".")` excludes search params and the hash of the resolved
-  // URL. This is the intended behavior of when "." is specifically provided as
+  // `useResolvedPath(".")` excludes search params of the resolved URL. This is
+  // the intended behavior of when "." is specifically provided as
   // the form action, but inconsistent w/ browsers when the action is omitted.
   // https://github.com/remix-run/remix/issues/927
   let location = useLocation();
   if (action == null) {
-    // Safe to write to these directly here since if action was undefined, we
+    // Safe to write to this directly here since if action was undefined, we
     // would have called useResolvedPath(".") which will never include a search
-    // or hash
     path.search = location.search;
-    path.hash = location.hash;
 
     // When grabbing search params from the URL, remove the automatically
     // inserted ?index param so we match the useResolvedPath search behavior