diff --git a/packages/flutter/lib/src/material/dropdown_menu.dart b/packages/flutter/lib/src/material/dropdown_menu.dart
index 45f3a38e3f8..0fcb87f0a04 100644
--- a/packages/flutter/lib/src/material/dropdown_menu.dart
+++ b/packages/flutter/lib/src/material/dropdown_menu.dart
@@ -1110,6 +1110,7 @@ class _DropdownMenuState<T> extends State<DropdownMenu<T>> {
     Widget menuAnchor = MenuAnchor(
       style: effectiveMenuStyle,
       alignmentOffset: widget.alignmentOffset,
+      reservedPadding: EdgeInsets.zero,
       controller: _controller,
       menuChildren: menu,
       crossAxisUnconstrained: false,
diff --git a/packages/flutter/lib/src/material/menu_anchor.dart b/packages/flutter/lib/src/material/menu_anchor.dart
index bb7ee3597b8..72793e83210 100644
--- a/packages/flutter/lib/src/material/menu_anchor.dart
+++ b/packages/flutter/lib/src/material/menu_anchor.dart
@@ -161,6 +161,7 @@ class MenuAnchor extends StatefulWidget {
     this.childFocusNode,
     this.style,
     this.alignmentOffset = Offset.zero,
+    this.reservedPadding,
     this.layerLink,
     this.clipBehavior = Clip.hardEdge,
     @Deprecated(
@@ -318,6 +319,11 @@ class MenuAnchor extends StatefulWidget {
   /// to rebuild this child when those change.
   final Widget? child;
 
+  /// The padding between the edge of the safe area and the menu panel.
+  ///
+  /// Defaults to EdgeInsets.all(8).
+  final EdgeInsetsGeometry? reservedPadding;
+
   @override
   State<MenuAnchor> createState() => _MenuAnchorState();
 
@@ -406,6 +412,7 @@ class _MenuAnchorState extends State<MenuAnchor> {
       menuPosition: position,
       anchor: this,
       alignmentOffset: widget.alignmentOffset ?? Offset.zero,
+      reservedPadding: widget.reservedPadding ?? const EdgeInsets.all(_kMenuViewPadding),
     );
   }
 
@@ -2920,6 +2927,7 @@ class _MenuLayout extends SingleChildLayoutDelegate {
     required this.avoidBounds,
     required this.orientation,
     required this.parentOrientation,
+    required this.reservedPadding,
   });
 
   // Rectangle of underlying button, relative to the overlay's dimensions.
@@ -2951,13 +2959,14 @@ class _MenuLayout extends SingleChildLayoutDelegate {
   // The orientation of this menu's parent.
   final Axis parentOrientation;
 
+  // How close to the edge of the safe area the menu will be placed.
+  final EdgeInsetsGeometry reservedPadding;
+
   @override
   BoxConstraints getConstraintsForChild(BoxConstraints constraints) {
-    // The menu can be at most the size of the overlay minus _kMenuViewPadding
-    // pixels in each direction.
-    return BoxConstraints.loose(
-      constraints.biggest,
-    ).deflate(const EdgeInsets.all(_kMenuViewPadding));
+    // The menu can be at most the size of the overlay minus the view padding
+    // in each direction.
+    return BoxConstraints.loose(constraints.biggest).deflate(reservedPadding);
   }
 
   @override
@@ -3289,6 +3298,7 @@ class _Submenu extends StatelessWidget {
     this.crossAxisUnconstrained = true,
     required this.menuChildren,
     required this.menuScopeNode,
+    required this.reservedPadding,
   });
 
   final FocusScopeNode menuScopeNode;
@@ -3301,6 +3311,7 @@ class _Submenu extends StatelessWidget {
   final Clip clipBehavior;
   final bool crossAxisUnconstrained;
   final List<Widget> menuChildren;
+  final EdgeInsetsGeometry reservedPadding;
 
   @override
   Widget build(BuildContext context) {
@@ -3399,6 +3410,7 @@ class _Submenu extends StatelessWidget {
                 menuPosition: menuPosition.position,
                 orientation: anchor._orientation,
                 parentOrientation: anchor._parent?._orientation ?? Axis.horizontal,
+                reservedPadding: reservedPadding,
               ),
               child: menuPanel,
             );
diff --git a/packages/flutter/test/material/dropdown_menu_test.dart b/packages/flutter/test/material/dropdown_menu_test.dart
index c2d4a54ecef..79f34540e8b 100644
--- a/packages/flutter/test/material/dropdown_menu_test.dart
+++ b/packages/flutter/test/material/dropdown_menu_test.dart
@@ -927,6 +927,31 @@ void main() {
     expect(buttonSize.width, parentWidth - 35.0 - 20.0);
   });
 
+  // Regression test for https://github.com/flutter/flutter/issues/172680.
+  testWidgets('Menu panel width can expand to full-screen width', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Scaffold(
+          body: DropdownMenu<int>(
+            expandedInsets: EdgeInsets.zero,
+            dropdownMenuEntries: <DropdownMenuEntry<int>>[
+              DropdownMenuEntry<int>(value: 0, label: 'Flutter'),
+            ],
+          ),
+        ),
+      ),
+    );
+
+    final double dropdownWidth = tester.getSize(find.byType(DropdownMenu<int>)).width;
+    expect(dropdownWidth, 800);
+
+    await tester.tap(find.byType(DropdownMenu<int>));
+    await tester.pump();
+
+    final double menuWidth = tester.getSize(findMenuItemButton('Flutter')).width;
+    expect(dropdownWidth, menuWidth);
+  });
+
   testWidgets(
     'Material2 - The menuHeight property can be used to show a shorter scrollable menu list instead of the complete list',
     (WidgetTester tester) async {
diff --git a/packages/flutter/test/material/menu_anchor_test.dart b/packages/flutter/test/material/menu_anchor_test.dart
index 9a7b950c7d0..7ef98382433 100644
--- a/packages/flutter/test/material/menu_anchor_test.dart
+++ b/packages/flutter/test/material/menu_anchor_test.dart
@@ -5047,6 +5047,55 @@ void main() {
       expect(find.byIcon(disabledIcon), findsOneWidget);
     });
   });
+
+  testWidgets('Menu panel default reserved padding', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Center(
+            child: MenuAnchor(
+              controller: controller,
+              menuChildren: const <Widget>[SizedBox(width: 800, height: 24)],
+              builder: (BuildContext context, MenuController controller, Widget? child) {
+                return const SizedBox(width: 800, height: 24);
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    controller.open();
+    await tester.pump();
+
+    const double defaultReservedPadding = 8.0; // See _kMenuViewPadding.
+    expect(tester.getRect(findMenuPanels()).width, 800.0 - defaultReservedPadding * 2);
+  });
+
+  testWidgets('Menu panel accepts custom reserved padding', (WidgetTester tester) async {
+    const EdgeInsetsGeometry reservedPadding = EdgeInsets.symmetric(horizontal: 13.0);
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Center(
+            child: MenuAnchor(
+              controller: controller,
+              reservedPadding: reservedPadding,
+              menuChildren: const <Widget>[SizedBox(width: 800, height: 24)],
+              builder: (BuildContext context, MenuController controller, Widget? child) {
+                return const SizedBox(width: 800, height: 24);
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    controller.open();
+    await tester.pump();
+
+    expect(tester.getRect(findMenuPanels()).width, 800.0 - reservedPadding.horizontal);
+  });
 }
 
 List<Widget> createTestMenus({