diff --git a/.changeset/mobilenav-toggle-expanded.md b/.changeset/mobilenav-toggle-expanded.md
new file mode 100644
index 000000000000..69b24acdd982
--- /dev/null
+++ b/.changeset/mobilenav-toggle-expanded.md
@@ -0,0 +1,6 @@
+---
+'@astryxdesign/core': patch
+---
+
+[fix] MobileNav: the toggle button now exposes `aria-expanded` and references the nav drawer via `aria-controls`, so screen-reader users can tell whether the drawer is open and what the button controls. (#3721)
+@bhamodi
diff --git a/packages/cli/templates/blocks/components/MobileNavToggle/MobileNavToggleBasic.tsx b/packages/cli/templates/blocks/components/MobileNavToggle/MobileNavToggleBasic.tsx
index cc04a2b60e5d..3b11466eecea 100644
--- a/packages/cli/templates/blocks/components/MobileNavToggle/MobileNavToggleBasic.tsx
+++ b/packages/cli/templates/blocks/components/MobileNavToggle/MobileNavToggleBasic.tsx
@@ -17,6 +17,7 @@ export default function MobileNavToggleBasic() {
       value={{
         isMobile: true,
         isMobileNavOpen: isOpen,
+        mobileNavId: 'demo-mobile-nav',
         toggleMobileNav: () => setIsOpen(v => !v),
         openMobileNav: () => setIsOpen(true),
         closeMobileNav: () => setIsOpen(false),
diff --git a/packages/cli/templates/blocks/components/MobileNavToggle/MobileNavToggleShowcase.tsx b/packages/cli/templates/blocks/components/MobileNavToggle/MobileNavToggleShowcase.tsx
index 4291175a9a77..33329f48e46a 100644
--- a/packages/cli/templates/blocks/components/MobileNavToggle/MobileNavToggleShowcase.tsx
+++ b/packages/cli/templates/blocks/components/MobileNavToggle/MobileNavToggleShowcase.tsx
@@ -16,6 +16,7 @@ export default function MobileNavToggleShowcase() {
       value={{
         isMobile: true,
         isMobileNavOpen: isOpen,
+        mobileNavId: 'demo-mobile-nav',
         toggleMobileNav: () => setIsOpen(v => !v),
         openMobileNav: () => setIsOpen(true),
         closeMobileNav: () => setIsOpen(false),
@@ -28,10 +29,7 @@ export default function MobileNavToggleShowcase() {
           Page title
         </Text>
       </HStack>
-      <MobileNav
-        isOpen={isOpen}
-        onOpenChange={setIsOpen}
-        header="Navigation">
+      <MobileNav isOpen={isOpen} onOpenChange={setIsOpen} header="Navigation">
         <SideNavSection title="Pages">
           <SideNavItem label="Home" isSelected href="#" />
           <SideNavItem label="Settings" href="#" />
diff --git a/packages/core/src/AppShell/AppShell.tsx b/packages/core/src/AppShell/AppShell.tsx
index 890ef05c6c74..e5244c414a67 100644
--- a/packages/core/src/AppShell/AppShell.tsx
+++ b/packages/core/src/AppShell/AppShell.tsx
@@ -24,6 +24,7 @@ import {
   isValidElement,
   useCallback,
   useEffect,
+  useId,
   useMemo,
   useRef,
   useState,
@@ -597,10 +598,14 @@ export function AppShell({
   // =========================================================================
   // Mobile context — shared with MobileNavToggle and future TopNav mobile
   // =========================================================================
+  // Stable id shared by the drawer (applied as its `id`) and the toggle
+  // (referenced via `aria-controls`) so screen readers know what it controls.
+  const mobileNavId = useId();
   const mobileContextValue = useMemo<AppShellMobileContextValue>(
     () => ({
       isMobile: isBelowBreakpoint,
       isMobileNavOpen,
+      mobileNavId,
       toggleMobileNav: () =>
         mobileNavEnabled && setMobileNavOpen(!isMobileNavOpen),
       openMobileNav: () => mobileNavEnabled && setMobileNavOpen(true),
@@ -611,6 +616,7 @@ export function AppShell({
     [
       isBelowBreakpoint,
       isMobileNavOpen,
+      mobileNavId,
       setMobileNavOpen,
       mobileNavEnabled,
       mobileNavHasToggle,
diff --git a/packages/core/src/AppShell/AppShellMobileContext.tsx b/packages/core/src/AppShell/AppShellMobileContext.tsx
index 99d9dec12598..af3f80911b15 100644
--- a/packages/core/src/AppShell/AppShellMobileContext.tsx
+++ b/packages/core/src/AppShell/AppShellMobileContext.tsx
@@ -20,6 +20,11 @@ export interface AppShellMobileContextValue {
   isMobile: boolean;
   /** Whether the mobile nav drawer is currently open */
   isMobileNavOpen: boolean;
+  /**
+   * DOM id of the mobile nav drawer. Shared so the toggle can point its
+   * `aria-controls` at the drawer and the drawer can apply it as its `id`.
+   */
+  mobileNavId: string;
   /** Toggle the mobile nav drawer open/closed */
   toggleMobileNav: () => void;
   /** Open the mobile nav drawer */
@@ -35,6 +40,7 @@ export interface AppShellMobileContextValue {
 const defaultValue: AppShellMobileContextValue = {
   isMobile: false,
   isMobileNavOpen: false,
+  mobileNavId: '',
   toggleMobileNav: () => {},
   openMobileNav: () => {},
   closeMobileNav: () => {},
diff --git a/packages/core/src/AppShell/useAppShellMobile.doc.mjs b/packages/core/src/AppShell/useAppShellMobile.doc.mjs
index 8d86e8a779b9..7c2e0fbdbe22 100644
--- a/packages/core/src/AppShell/useAppShellMobile.doc.mjs
+++ b/packages/core/src/AppShell/useAppShellMobile.doc.mjs
@@ -31,6 +31,12 @@ export const docs = {
       description:
         'Whether the AppShell-managed mobile navigation drawer is open.',
     },
+    {
+      name: 'mobileNavId',
+      type: 'string',
+      description:
+        'DOM id of the mobile navigation drawer. Point aria-controls of a custom toggle at this so screen-reader users know which element the toggle expands.',
+    },
     {
       name: 'toggleMobileNav',
       type: '() => void',
@@ -111,6 +117,8 @@ export const docsDense = {
     isMobile:
       'viewport below AppShell mobile nav breakpoint? Use to sync AppShell-adjacent mobile UI',
     isMobileNavOpen: 'AppShell-managed mobile nav drawer open?',
+    mobileNavId:
+      'DOM id of the drawer; point custom toggle aria-controls at it',
     toggleMobileNav: 'toggle drawer; no-op when mobile nav disabled',
     openMobileNav: 'open drawer; no-op when mobile nav disabled',
     closeMobileNav: 'close drawer',
diff --git a/packages/core/src/MobileNav/MobileNav.tsx b/packages/core/src/MobileNav/MobileNav.tsx
index 2256186b9f58..a6084609952d 100644
--- a/packages/core/src/MobileNav/MobileNav.tsx
+++ b/packages/core/src/MobileNav/MobileNav.tsx
@@ -29,6 +29,7 @@
 import {
   useCallback,
   useEffect,
+  useId,
   useMemo,
   useRef,
   useState,
@@ -291,6 +292,10 @@ export function MobileNav({
   // Read from AppShell context as fallback
   const appShellMobile = useAppShellMobile();
   const isOpen = isOpenProp ?? appShellMobile.isMobileNavOpen;
+  // Share the id from AppShell context so the toggle's aria-controls resolves to
+  // this drawer; fall back to a locally generated id when used standalone.
+  const fallbackId = useId();
+  const dialogId = appShellMobile.mobileNavId || fallbackId;
   const onOpenChange = useMemo(
     () =>
       onOpenChangeProp ??
@@ -407,6 +412,7 @@ export function MobileNav({
   return (
     <dialog
       ref={mergeRefs(ref, dialogRef)}
+      id={dialogId}
       data-testid={testId}
       aria-label={label ?? (typeof header === 'string' ? header : 'Navigation')}
       onClick={handleDialogClick}
diff --git a/packages/core/src/MobileNav/MobileNavToggle.test.tsx b/packages/core/src/MobileNav/MobileNavToggle.test.tsx
new file mode 100644
index 000000000000..fb1bf4825b60
--- /dev/null
+++ b/packages/core/src/MobileNav/MobileNavToggle.test.tsx
@@ -0,0 +1,116 @@
+// Copyright (c) Meta Platforms, Inc. and affiliates.
+
+/**
+ * @file MobileNavToggle.test.tsx
+ * @input Uses vitest, @testing-library/react, AppShell + SideNav
+ * @output Unit tests for MobileNavToggle ARIA wiring
+ * @position Testing; validates MobileNavToggle.tsx exposes aria-expanded and
+ *   aria-controls so screen-reader users know the drawer state and target.
+ *
+ * SYNC: When MobileNavToggle.tsx changes, update tests to match new behavior
+ */
+
+import {
+  describe,
+  it,
+  expect,
+  vi,
+  beforeAll,
+  beforeEach,
+  afterEach,
+} from 'vitest';
+import {render, screen, fireEvent} from '@testing-library/react';
+import {AppShell} from '../AppShell/AppShell';
+import {SideNav, SideNavItem, SideNavSection} from '../SideNav';
+
+// jsdom doesn't implement showModal/close on <dialog>, so we mock them
+beforeAll(() => {
+  HTMLDialogElement.prototype.showModal =
+    HTMLDialogElement.prototype.showModal ||
+    function (this: HTMLDialogElement) {
+      this.setAttribute('open', '');
+    };
+  HTMLDialogElement.prototype.close =
+    HTMLDialogElement.prototype.close ||
+    function (this: HTMLDialogElement) {
+      this.removeAttribute('open');
+    };
+});
+
+class MockResizeObserver {
+  observe() {}
+  unobserve() {}
+  disconnect() {}
+}
+vi.stubGlobal('ResizeObserver', MockResizeObserver);
+
+function createMockMatchMedia(matches: boolean) {
+  return {
+    matches,
+    media: '',
+    onchange: null,
+    addEventListener: vi.fn(),
+    removeEventListener: vi.fn(),
+    addListener: vi.fn(),
+    removeListener: vi.fn(),
+    dispatchEvent: vi.fn(),
+  };
+}
+
+beforeEach(() => {
+  // Below the breakpoint so the mobile nav (and its toggle) render.
+  vi.stubGlobal(
+    'matchMedia',
+    vi.fn().mockReturnValue(createMockMatchMedia(true)),
+  );
+});
+
+afterEach(() => {
+  vi.restoreAllMocks();
+});
+
+function TestShell() {
+  return (
+    <AppShell
+      sideNav={
+        <SideNav>
+          <SideNavSection title="Test" isHeaderHidden>
+            <SideNavItem label="Home" />
+          </SideNavSection>
+        </SideNav>
+      }
+      mobileNav={{breakpoint: 'md'}}>
+      <div>Content</div>
+    </AppShell>
+  );
+}
+
+describe('MobileNavToggle ARIA wiring', () => {
+  it('exposes aria-expanded="false" when the drawer is closed', () => {
+    render(<TestShell />);
+
+    const toggle = screen.getByRole('button', {name: /open navigation/i});
+    expect(toggle).toHaveAttribute('aria-expanded', 'false');
+  });
+
+  it('exposes aria-expanded="true" after opening the drawer', () => {
+    render(<TestShell />);
+
+    const toggle = screen.getByRole('button', {name: /open navigation/i});
+    fireEvent.click(toggle);
+    expect(toggle).toHaveAttribute('aria-expanded', 'true');
+  });
+
+  it('references the nav drawer via aria-controls that resolves to the dialog', () => {
+    render(<TestShell />);
+
+    const toggle = screen.getByRole('button', {name: /open navigation/i});
+    const controls = toggle.getAttribute('aria-controls');
+    expect(controls).toBeTruthy();
+
+    const target = document.getElementById(controls!);
+    expect(target).not.toBeNull();
+    expect(target).toBe(screen.getAllByRole('dialog', {hidden: true})[0]);
+    expect(target?.tagName).toBe('DIALOG');
+  });
+});
diff --git a/packages/core/src/MobileNav/MobileNavToggle.tsx b/packages/core/src/MobileNav/MobileNavToggle.tsx
index 61d88aed254f..83688e24f610 100644
--- a/packages/core/src/MobileNav/MobileNavToggle.tsx
+++ b/packages/core/src/MobileNav/MobileNavToggle.tsx
@@ -66,8 +66,13 @@ export function MobileNavToggle({
   className,
   style,
 }: MobileNavToggleProps) {
-  const {isMobile, isMobileNavEnabled, toggleMobileNav} =
-    useAppShellMobile();
+  const {
+    isMobile,
+    isMobileNavEnabled,
+    isMobileNavOpen,
+    mobileNavId,
+    toggleMobileNav,
+  } = useAppShellMobile();
 
   // Don't render above the breakpoint or when mobile nav is disabled
   if (!isMobile || !isMobileNavEnabled) {
@@ -81,6 +86,8 @@ export function MobileNavToggle({
       label={label}
       icon={children ?? <Icon icon="menu" color="inherit" />}
       onClick={toggleMobileNav}
+      aria-expanded={isMobileNavOpen}
+      aria-controls={mobileNavId || undefined}
       data-testid={testId ?? 'mobile-nav-toggle'}
       xstyle={xstyle}
       className={className}
diff --git a/packages/core/src/SideNav/SideNav.test.tsx b/packages/core/src/SideNav/SideNav.test.tsx
index 6c75c34105aa..5ace77041f92 100644
--- a/packages/core/src/SideNav/SideNav.test.tsx
+++ b/packages/core/src/SideNav/SideNav.test.tsx
@@ -1117,6 +1117,7 @@ describe('SideNavItem — mobile drawer close-on-activate', () => {
           value={{
             isMobile: true,
             isMobileNavOpen: true,
+            mobileNavId: 'test-mobile-nav',
             toggleMobileNav: vi.fn(),
             openMobileNav: vi.fn(),
             closeMobileNav,
@@ -1172,6 +1173,7 @@ describe('SideNavItem — mobile drawer close-on-activate', () => {
         value={{
           isMobile: false,
           isMobileNavOpen: false,
+          mobileNavId: 'test-mobile-nav',
           toggleMobileNav: vi.fn(),
           openMobileNav: vi.fn(),
           closeMobileNav,