diff --git a/change/@fluentui-react-headless-components-preview-b0360dff-28bf-4dcc-9d25-d07a2ae536ec.json b/change/@fluentui-react-headless-components-preview-b0360dff-28bf-4dcc-9d25-d07a2ae536ec.json
new file mode 100644
index 00000000000000..b3625c629bca1f
--- /dev/null
+++ b/change/@fluentui-react-headless-components-preview-b0360dff-28bf-4dcc-9d25-d07a2ae536ec.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: MenuSplitGroup provides its context to descendants via a new exported useMenuSplitGroupContextValues hook",
+  "packageName": "@fluentui/react-headless-components-preview",
+  "email": "array.knight@gmail.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/react-components/react-headless-components-preview/library/etc/menu.api.md b/packages/react-components/react-headless-components-preview/library/etc/menu.api.md
index d5795fe2182ec6..47225a7d4c8ab4 100644
--- a/packages/react-components/react-headless-components-preview/library/etc/menu.api.md
+++ b/packages/react-components/react-headless-components-preview/library/etc/menu.api.md
@@ -191,6 +191,13 @@ export type MenuProps = Omit<MenuBaseProps, 'positioning'> & {
 // @public (undocumented)
 export const MenuSplitGroup: ForwardRefComponent<MenuSplitGroupProps>;
 
+// @public
+export type MenuSplitGroupContextValues = {
+    menuSplitGroup: {
+        setMultiline: (multiline: boolean) => void;
+    };
+};
+
 export { MenuSplitGroupProps }
 
 export { MenuSplitGroupSlots }
@@ -279,6 +286,9 @@ export const useMenuPopover: (props: MenuPopoverProps, ref: React_2.Ref<HTMLElem
 // @public
 export const useMenuSplitGroup: (props: MenuSplitGroupProps, ref: React_2.Ref<HTMLElement>) => MenuSplitGroupState;
 
+// @public
+export const useMenuSplitGroupContextValues: (state: MenuSplitGroupState) => MenuSplitGroupContextValues;
+
 // @public (undocumented)
 export const useMenuTrigger: (props: MenuTriggerProps) => MenuTriggerState;
 
diff --git a/packages/react-components/react-headless-components-preview/library/src/components/Menu/Menu.test.tsx b/packages/react-components/react-headless-components-preview/library/src/components/Menu/Menu.test.tsx
index d5dc4f9b44fed9..be5399657cf518 100644
--- a/packages/react-components/react-headless-components-preview/library/src/components/Menu/Menu.test.tsx
+++ b/packages/react-components/react-headless-components-preview/library/src/components/Menu/Menu.test.tsx
@@ -13,6 +13,7 @@ import { MenuItemSwitch } from './MenuItemSwitch/MenuItemSwitch';
 import { MenuDivider } from './MenuDivider/MenuDivider';
 import { MenuGroup } from './MenuGroup/MenuGroup';
 import { MenuGroupHeader } from './MenuGroupHeader/MenuGroupHeader';
+import { MenuSplitGroup } from './MenuSplitGroup/MenuSplitGroup';
 
 describe('Menu', () => {
   it('renders trigger and surface children when open', () => {
@@ -502,4 +503,39 @@ describe('Menu', () => {
       expect(header.getAttribute('id')).toBeTruthy();
     });
   });
+
+  describe('MenuSplitGroup', () => {
+    // Regression test for https://github.com/microsoft/fluentui/issues/36651 — MenuSplitGroup
+    // rendered without a contexts argument, so `useIsInMenuSplitGroup` could never return true and
+    // descendants kept the icon gutter that a split-group trigger is supposed to drop.
+    it('provides split group context so the trigger half drops the icon gutter', () => {
+      const { getByTestId } = render(
+        <Menu defaultOpen>
+          <MenuTrigger>
+            <button>Trigger</button>
+          </MenuTrigger>
+          <MenuPopover>
+            <MenuList hasIcons>
+              <MenuItem hasSubmenu data-testid="outside-item">
+                Outside
+              </MenuItem>
+              <MenuSplitGroup data-testid="split-group">
+                <MenuItem hasSubmenu data-testid="split-trigger">
+                  Split main
+                </MenuItem>
+                <MenuItem data-testid="split-chevron">Chevron</MenuItem>
+              </MenuSplitGroup>
+            </MenuList>
+          </MenuPopover>
+        </Menu>,
+      );
+
+      expect(getByTestId('split-group')).toHaveAttribute('role', 'group');
+
+      // Outside the split group: default icon gutter + submenu indicator + content = 3 spans.
+      expect(getByTestId('outside-item').querySelectorAll('span')).toHaveLength(3);
+      // Inside the split group the trigger half suppresses the icon gutter: indicator + content.
+      expect(getByTestId('split-trigger').querySelectorAll('span')).toHaveLength(2);
+    });
+  });
 });
diff --git a/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/MenuSplitGroup.tsx b/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/MenuSplitGroup.tsx
index 71c98981325439..2b7c7fb507558e 100644
--- a/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/MenuSplitGroup.tsx
+++ b/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/MenuSplitGroup.tsx
@@ -3,12 +3,15 @@
 import * as React from 'react';
 import type { ForwardRefComponent } from '@fluentui/react-utilities';
 import { useMenuSplitGroup } from './useMenuSplitGroup';
+import { useMenuSplitGroupContextValues } from './useMenuSplitGroupContextValues';
 import { renderMenuSplitGroup } from './renderMenuSplitGroup';
 import type { MenuSplitGroupProps } from '@fluentui/react-menu';
 
 export const MenuSplitGroup: ForwardRefComponent<MenuSplitGroupProps> = React.forwardRef((props, ref) => {
   const state = useMenuSplitGroup(props, ref);
-  return renderMenuSplitGroup(state);
+  const contextValues = useMenuSplitGroupContextValues(state);
+
+  return renderMenuSplitGroup(state, contextValues);
 });
 
 MenuSplitGroup.displayName = 'MenuSplitGroup';
diff --git a/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/index.ts b/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/index.ts
index 4c8a5cf3d09f46..496dc867919fef 100644
--- a/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/index.ts
+++ b/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/index.ts
@@ -1,4 +1,6 @@
 export { MenuSplitGroup } from './MenuSplitGroup';
 export { useMenuSplitGroup } from './useMenuSplitGroup';
+export { useMenuSplitGroupContextValues } from './useMenuSplitGroupContextValues';
+export type { MenuSplitGroupContextValues } from './useMenuSplitGroupContextValues';
 export { renderMenuSplitGroup } from './renderMenuSplitGroup';
 export type { MenuSplitGroupProps, MenuSplitGroupSlots, MenuSplitGroupState } from '@fluentui/react-menu';
diff --git a/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/useMenuSplitGroupContextValues.ts b/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/useMenuSplitGroupContextValues.ts
new file mode 100644
index 00000000000000..70bc7c62cd874e
--- /dev/null
+++ b/packages/react-components/react-headless-components-preview/library/src/components/Menu/MenuSplitGroup/useMenuSplitGroupContextValues.ts
@@ -0,0 +1,31 @@
+'use client';
+
+import * as React from 'react';
+import type { MenuSplitGroupState } from '@fluentui/react-menu';
+
+/**
+ * Context values shared with the descendants of a MenuSplitGroup.
+ *
+ * Mirrors `@fluentui/react-menu`'s `MenuSplitGroupContextValues`, which that package does not
+ * export from its public API.
+ */
+export type MenuSplitGroupContextValues = {
+  menuSplitGroup: {
+    setMultiline: (multiline: boolean) => void;
+  };
+};
+
+/**
+ * Builds the context value shared with the descendants of a MenuSplitGroup.
+ *
+ * `useIsInMenuSplitGroup` compares the provided value against the module-level default by
+ * identity, so providing one is what lets a descendant tell it is inside a split group. The memo
+ * keeps that identity stable across renders; `setMultiline` stays the documented no-op.
+ */
+export const useMenuSplitGroupContextValues = (state: MenuSplitGroupState): MenuSplitGroupContextValues => {
+  const { setMultiline } = state;
+
+  const menuSplitGroup = React.useMemo(() => ({ setMultiline }), [setMultiline]);
+
+  return { menuSplitGroup };
+};
diff --git a/packages/react-components/react-headless-components-preview/library/src/components/Menu/index.ts b/packages/react-components/react-headless-components-preview/library/src/components/Menu/index.ts
index c236c4f3a82f2f..3d0a3baa804627 100644
--- a/packages/react-components/react-headless-components-preview/library/src/components/Menu/index.ts
+++ b/packages/react-components/react-headless-components-preview/library/src/components/Menu/index.ts
@@ -45,5 +45,11 @@ export type { MenuGroupProps, MenuGroupSlots, MenuGroupState, MenuGroupContextVa
 export { MenuGroupHeader, useMenuGroupHeader, renderMenuGroupHeader } from './MenuGroupHeader';
 export type { MenuGroupHeaderProps, MenuGroupHeaderSlots, MenuGroupHeaderState } from '@fluentui/react-menu';
 
-export { MenuSplitGroup, useMenuSplitGroup, renderMenuSplitGroup } from './MenuSplitGroup';
+export {
+  MenuSplitGroup,
+  useMenuSplitGroup,
+  useMenuSplitGroupContextValues,
+  renderMenuSplitGroup,
+} from './MenuSplitGroup';
+export type { MenuSplitGroupContextValues } from './MenuSplitGroup';
 export type { MenuSplitGroupProps, MenuSplitGroupSlots, MenuSplitGroupState } from '@fluentui/react-menu';
diff --git a/packages/react-components/react-headless-components-preview/library/src/menu.ts b/packages/react-components/react-headless-components-preview/library/src/menu.ts
index 108d8ff6180565..10f1fb4a538596 100644
--- a/packages/react-components/react-headless-components-preview/library/src/menu.ts
+++ b/packages/react-components/react-headless-components-preview/library/src/menu.ts
@@ -41,6 +41,7 @@ export {
   renderMenuGroupHeader,
   MenuSplitGroup,
   useMenuSplitGroup,
+  useMenuSplitGroupContextValues,
   renderMenuSplitGroup,
 } from './components/Menu';
 export type {
@@ -85,4 +86,5 @@ export type {
   MenuSplitGroupProps,
   MenuSplitGroupSlots,
   MenuSplitGroupState,
+  MenuSplitGroupContextValues,
 } from './components/Menu';