diff --git a/Libraries/LibGUI/GMenu.cpp b/Libraries/LibGUI/GMenu.cpp
index b2940768f5..9be1fc53d6 100644
--- a/Libraries/LibGUI/GMenu.cpp
+++ b/Libraries/LibGUI/GMenu.cpp
@@ -39,15 +39,25 @@ void GMenu::add_action(NonnullRefPtr<GAction> action)
 #endif
 }
 
+void GMenu::add_submenu(NonnullOwnPtr<GMenu> submenu)
+{
+    m_items.append(make<GMenuItem>(m_menu_id, move(submenu)));
+}
+
 void GMenu::add_separator()
 {
     m_items.append(make<GMenuItem>(m_menu_id, GMenuItem::Separator));
 }
 
-void GMenu::popup(const Point& screen_position)
+void GMenu::realize_if_needed()
 {
     if (m_menu_id == -1)
         realize_menu();
+}
+
+void GMenu::popup(const Point& screen_position)
+{
+    realize_if_needed();
     WSAPI_ClientMessage request;
     request.type = WSAPI_ClientMessage::Type::PopupMenu;
     request.menu.menu_id = m_menu_id;
@@ -87,14 +97,34 @@ int GMenu::realize_menu()
             WSAPI_ClientMessage request;
             request.type = WSAPI_ClientMessage::Type::AddMenuSeparator;
             request.menu.menu_id = m_menu_id;
+            request.menu.submenu_id = -1;
             GWindowServerConnection::the().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuSeparator);
             continue;
         }
+        if (item.type() == GMenuItem::Submenu) {
+            auto& submenu = *item.submenu();
+            submenu.realize_if_needed();
+            WSAPI_ClientMessage request;
+            request.type = WSAPI_ClientMessage::Type::AddMenuItem;
+            request.menu.menu_id = m_menu_id;
+            request.menu.submenu_id = submenu.menu_id();
+            request.menu.identifier = i;
+            // FIXME: It should be possible to disable a submenu.
+            request.menu.enabled = true;
+            request.menu.checkable = false;
+            request.menu.checked = false;
+            ASSERT(submenu.name().length() < (ssize_t)sizeof(request.text));
+            strcpy(request.text, submenu.name().characters());
+            request.text_length = submenu.name().length();
+            GWindowServerConnection::the().sync_request(request, WSAPI_ServerMessage::Type::DidAddMenuItem);
+            continue;
+        }
         if (item.type() == GMenuItem::Action) {
             auto& action = *item.action();
             WSAPI_ClientMessage request;
             request.type = WSAPI_ClientMessage::Type::AddMenuItem;
             request.menu.menu_id = m_menu_id;
+            request.menu.submenu_id = -1;
             request.menu.identifier = i;
             request.menu.enabled = action.is_enabled();
             request.menu.checkable = action.is_checkable();
diff --git a/Libraries/LibGUI/GMenu.h b/Libraries/LibGUI/GMenu.h
index 2ddd6f41f2..f873c92def 100644
--- a/Libraries/LibGUI/GMenu.h
+++ b/Libraries/LibGUI/GMenu.h
@@ -15,10 +15,13 @@ public:
 
     static GMenu* from_menu_id(int);
 
+    const String& name() const { return m_name; }
+
     GAction* action_at(int);
 
     void add_action(NonnullRefPtr<GAction>);
     void add_separator();
+    void add_submenu(NonnullOwnPtr<GMenu>);
 
     void popup(const Point& screen_position);
     void dismiss();
@@ -31,6 +34,7 @@ private:
     int menu_id() const { return m_menu_id; }
     int realize_menu();
     void unrealize_menu();
+    void realize_if_needed();
 
     int m_menu_id { -1 };
     String m_name;
diff --git a/Libraries/LibGUI/GMenuItem.cpp b/Libraries/LibGUI/GMenuItem.cpp
index 3007d560f0..2da0200ca3 100644
--- a/Libraries/LibGUI/GMenuItem.cpp
+++ b/Libraries/LibGUI/GMenuItem.cpp
@@ -1,5 +1,6 @@
 #include <LibGUI/GAction.h>
 #include <LibGUI/GEventLoop.h>
+#include <LibGUI/GMenu.h>
 #include <LibGUI/GMenuItem.h>
 #include <WindowServer/WSAPITypes.h>
 
@@ -21,6 +22,13 @@ GMenuItem::GMenuItem(unsigned menu_id, NonnullRefPtr<GAction>&& action)
         m_checked = m_action->is_checked();
 }
 
+GMenuItem::GMenuItem(unsigned menu_id, NonnullOwnPtr<GMenu>&& submenu)
+    : m_type(Submenu)
+    , m_menu_id(menu_id)
+    , m_submenu(move(submenu))
+{
+}
+
 GMenuItem::~GMenuItem()
 {
     if (m_action)
diff --git a/Libraries/LibGUI/GMenuItem.h b/Libraries/LibGUI/GMenuItem.h
index 092b2c9fe0..73fa8bcdad 100644
--- a/Libraries/LibGUI/GMenuItem.h
+++ b/Libraries/LibGUI/GMenuItem.h
@@ -2,6 +2,8 @@
 
 #include <AK/AKString.h>
 #include <AK/Badge.h>
+#include <AK/NonnullOwnPtr.h>
+#include <AK/OwnPtr.h>
 
 class GAction;
 class GMenu;
@@ -11,11 +13,13 @@ public:
     enum Type {
         Invalid,
         Action,
-        Separator
+        Separator,
+        Submenu,
     };
 
     GMenuItem(unsigned menu_id, Type);
     GMenuItem(unsigned menu_id, NonnullRefPtr<GAction>&&);
+    GMenuItem(unsigned menu_id, NonnullOwnPtr<GMenu>&&);
     ~GMenuItem();
 
     Type type() const { return m_type; }
@@ -24,6 +28,9 @@ public:
     GAction* action() { return m_action.ptr(); }
     unsigned identifier() const { return m_identifier; }
 
+    GMenu* submenu() { return m_submenu.ptr(); }
+    const GMenu* submenu() const { return m_submenu.ptr(); }
+
     bool is_checkable() const { return m_checkable; }
     void set_checkable(bool checkable) { m_checkable = checkable; }
 
@@ -46,4 +53,5 @@ private:
     bool m_checkable { false };
     bool m_checked { false };
     RefPtr<GAction> m_action;
+    OwnPtr<GMenu> m_submenu;
 };
diff --git a/Servers/WindowServer/WSAPITypes.h b/Servers/WindowServer/WSAPITypes.h
index be7eb0ef43..4d5e7574db 100644
--- a/Servers/WindowServer/WSAPITypes.h
+++ b/Servers/WindowServer/WSAPITypes.h
@@ -263,6 +263,7 @@ struct WSAPI_ClientMessage {
         struct {
             int menubar_id;
             int menu_id;
+            int submenu_id;
             int icon_buffer_id;
             unsigned identifier;
             char shortcut_text[32];
diff --git a/Servers/WindowServer/WSClientConnection.cpp b/Servers/WindowServer/WSClientConnection.cpp
index 154fdc015b..c71215473a 100644
--- a/Servers/WindowServer/WSClientConnection.cpp
+++ b/Servers/WindowServer/WSClientConnection.cpp
@@ -159,7 +159,7 @@ bool WSClientConnection::handle_message(const WSAPI_ClientMessage& message, cons
             did_misbehave();
             return false;
         }
-        CEventLoop::current().post_event(*this, make<WSAPIAddMenuItemRequest>(client_id(), message.menu.menu_id, message.menu.identifier, String(message.text, message.text_length), String(message.menu.shortcut_text, message.menu.shortcut_text_length), message.menu.enabled, message.menu.checkable, message.menu.checked, message.menu.icon_buffer_id));
+        CEventLoop::current().post_event(*this, make<WSAPIAddMenuItemRequest>(client_id(), message.menu.menu_id, message.menu.identifier, String(message.text, message.text_length), String(message.menu.shortcut_text, message.menu.shortcut_text_length), message.menu.enabled, message.menu.checkable, message.menu.checked, message.menu.icon_buffer_id, message.menu.submenu_id));
         break;
     case WSAPI_ClientMessage::Type::UpdateMenuItem:
         if (message.text_length > (int)sizeof(message.text)) {
@@ -434,6 +434,7 @@ void WSClientConnection::handle_request(const WSAPIAddMenuItemRequest& request)
         auto shared_icon = GraphicsBitmap::create_with_shared_buffer(GraphicsBitmap::Format::RGBA32, icon_buffer.release_nonnull(), { 16, 16 });
         menu_item->set_icon(shared_icon);
     }
+    menu_item->set_submenu_id(request.submenu_id());
     menu.add_item(move(menu_item));
     WSAPI_ServerMessage response;
     response.type = WSAPI_ServerMessage::Type::DidAddMenuItem;
diff --git a/Servers/WindowServer/WSClientConnection.h b/Servers/WindowServer/WSClientConnection.h
index 115951ecfa..16770464f7 100644
--- a/Servers/WindowServer/WSClientConnection.h
+++ b/Servers/WindowServer/WSClientConnection.h
@@ -37,6 +37,12 @@ public:
     void notify_about_new_screen_rect(const Rect&);
     void post_paint_message(WSWindow&);
 
+    WSMenu* find_menu_by_id(int menu_id)
+    {
+        // FIXME: Remove this const_cast when Optional knows how to vend a non-const fallback value somehow.
+        return const_cast<WSMenu*>(m_menus.get(menu_id).value_or(nullptr));
+    }
+
 private:
     virtual void event(CEvent&) override;
 
diff --git a/Servers/WindowServer/WSEvent.h b/Servers/WindowServer/WSEvent.h
index 215bc00fec..ab1083b5c6 100644
--- a/Servers/WindowServer/WSEvent.h
+++ b/Servers/WindowServer/WSEvent.h
@@ -303,7 +303,7 @@ private:
 
 class WSAPIAddMenuItemRequest : public WSAPIClientRequest {
 public:
-    WSAPIAddMenuItemRequest(int client_id, int menu_id, unsigned identifier, const String& text, const String& shortcut_text, bool enabled, bool checkable, bool checked, int icon_buffer_id)
+    WSAPIAddMenuItemRequest(int client_id, int menu_id, unsigned identifier, const String& text, const String& shortcut_text, bool enabled, bool checkable, bool checked, int icon_buffer_id, int submenu_id)
         : WSAPIClientRequest(WSEvent::APIAddMenuItemRequest, client_id)
         , m_menu_id(menu_id)
         , m_identifier(identifier)
@@ -313,6 +313,7 @@ public:
         , m_checkable(checkable)
         , m_checked(checked)
         , m_icon_buffer_id(icon_buffer_id)
+        , m_submenu_id(submenu_id)
     {
     }
 
@@ -324,6 +325,7 @@ public:
     bool is_checkable() const { return m_checkable; }
     bool is_checked() const { return m_checked; }
     int icon_buffer_id() const { return m_icon_buffer_id; }
+    int submenu_id() const { return m_submenu_id; }
 
 private:
     int m_menu_id { 0 };
@@ -334,6 +336,7 @@ private:
     bool m_checkable;
     bool m_checked;
     int m_icon_buffer_id { 0 };
+    int m_submenu_id { 0 };
 };
 
 class WSAPIUpdateMenuItemRequest : public WSAPIClientRequest {
diff --git a/Servers/WindowServer/WSMenu.cpp b/Servers/WindowServer/WSMenu.cpp
index 1484728e58..a57a7ace17 100644
--- a/Servers/WindowServer/WSMenu.cpp
+++ b/Servers/WindowServer/WSMenu.cpp
@@ -2,6 +2,7 @@
 #include "WSEvent.h"
 #include "WSEventLoop.h"
 #include "WSMenuItem.h"
+#include "WSMenuManager.h"
 #include "WSScreen.h"
 #include "WSWindow.h"
 #include "WSWindowManager.h"
@@ -42,9 +43,23 @@ static const char* s_checked_bitmap_data = {
     "         "
 };
 
+static const char* s_submenu_arrow_bitmap_data = {
+    "         "
+    "   #     "
+    "   ##    "
+    "   ###   "
+    "   ####  "
+    "   ###   "
+    "   ##    "
+    "   #     "
+    "         "
+};
+
 static CharacterBitmap* s_checked_bitmap;
 static const int s_checked_bitmap_width = 9;
 static const int s_checked_bitmap_height = 9;
+static const int s_submenu_arrow_bitmap_width = 9;
+static const int s_submenu_arrow_bitmap_height = 9;
 static const int s_item_icon_width = 16;
 static const int s_checkbox_or_icon_padding = 6;
 static const int s_stripe_width = 23;
@@ -163,6 +178,17 @@ void WSMenu::draw()
             if (!item.shortcut_text().is_empty()) {
                 painter.draw_text(item.rect().translated(-right_padding(), 0), item.shortcut_text(), TextAlignment::CenterRight, text_color);
             }
+            if (item.is_submenu()) {
+                static auto& submenu_arrow_bitmap = CharacterBitmap::create_from_ascii(s_submenu_arrow_bitmap_data, s_submenu_arrow_bitmap_width, s_submenu_arrow_bitmap_height).leak_ref();
+                Rect submenu_arrow_rect {
+                    item.rect().right() - s_submenu_arrow_bitmap_width - 2,
+                    0,
+                    s_submenu_arrow_bitmap_width,
+                    s_submenu_arrow_bitmap_height
+                };
+                submenu_arrow_rect.center_vertically_within(item.rect());
+                painter.draw_bitmap(submenu_arrow_rect.location(), submenu_arrow_bitmap, Color::Black);
+            }
         } else if (item.type() == WSMenuItem::Separator) {
             Point p1(item.rect().translated(stripe_rect.width() + 4, 0).x(), item.rect().center().y() - 1);
             Point p2(width - 7, item.rect().center().y() - 1);
@@ -180,6 +206,23 @@ void WSMenu::event(CEvent& event)
         if (!item || m_hovered_item == item)
             return;
         m_hovered_item = item;
+        if (m_hovered_item->is_submenu()) {
+            m_hovered_item->submenu()->popup(m_hovered_item->rect().top_right().translated(menu_window()->rect().location()), true);
+        } else {
+            bool close_remaining_menus = false;
+            for (auto& open_menu : WSWindowManager::the().menu_manager().open_menu_stack()) {
+                if (!open_menu)
+                    continue;
+                if (close_remaining_menus) {
+                    open_menu->menu_window()->set_visible(false);
+                    continue;
+                }
+                if (open_menu == this) {
+                    close_remaining_menus = true;
+                    continue;
+                }
+            }
+        }
         redraw();
         return;
     }
@@ -246,7 +289,7 @@ void WSMenu::close()
         menu_window()->set_visible(false);
 }
 
-void WSMenu::popup(const Point& position)
+void WSMenu::popup(const Point& position, bool is_submenu)
 {
     ASSERT(!is_empty());
 
@@ -262,5 +305,5 @@ void WSMenu::popup(const Point& position)
 
     window.move_to(adjusted_pos);
     window.set_visible(true);
-    WSWindowManager::the().set_current_menu(this);
+    WSWindowManager::the().set_current_menu(this, is_submenu);
 }
diff --git a/Servers/WindowServer/WSMenu.h b/Servers/WindowServer/WSMenu.h
index 8b0d437775..f57841f446 100644
--- a/Servers/WindowServer/WSMenu.h
+++ b/Servers/WindowServer/WSMenu.h
@@ -73,7 +73,7 @@ public:
 
     void close();
 
-    void popup(const Point&);
+    void popup(const Point&, bool is_submenu = false);
 
 private:
     virtual void event(CEvent&) override;
diff --git a/Servers/WindowServer/WSMenuItem.cpp b/Servers/WindowServer/WSMenuItem.cpp
index ba65e391e6..477497b9dc 100644
--- a/Servers/WindowServer/WSMenuItem.cpp
+++ b/Servers/WindowServer/WSMenuItem.cpp
@@ -1,4 +1,5 @@
 #include "WSMenuItem.h"
+#include "WSClientConnection.h"
 #include "WSMenu.h"
 #include <LibDraw/GraphicsBitmap.h>
 
@@ -40,3 +41,10 @@ void WSMenuItem::set_checked(bool checked)
     m_checked = checked;
     m_menu.redraw();
 }
+
+WSMenu* WSMenuItem::submenu()
+{
+    ASSERT(is_submenu());
+    ASSERT(m_menu.client());
+    return m_menu.client()->find_menu_by_id(m_submenu_id);
+}
diff --git a/Servers/WindowServer/WSMenuItem.h b/Servers/WindowServer/WSMenuItem.h
index 27b9595222..fe334b3c0d 100644
--- a/Servers/WindowServer/WSMenuItem.h
+++ b/Servers/WindowServer/WSMenuItem.h
@@ -44,6 +44,12 @@ public:
     const GraphicsBitmap* icon() const { return m_icon; }
     void set_icon(const GraphicsBitmap* icon) { m_icon = icon; }
 
+    bool is_submenu() const { return m_submenu_id != -1; }
+    int submenu_id() const { return m_submenu_id; }
+    void set_submenu_id(int submenu_id) { m_submenu_id = submenu_id; }
+
+    WSMenu* submenu();
+
 private:
     WSMenu& m_menu;
     Type m_type { None };
@@ -55,4 +61,5 @@ private:
     String m_shortcut_text;
     Rect m_rect;
     RefPtr<GraphicsBitmap> m_icon;
+    int m_submenu_id { -1 };
 };
diff --git a/Servers/WindowServer/WSMenuManager.cpp b/Servers/WindowServer/WSMenuManager.cpp
index 3f31e6197d..8fb805cba1 100644
--- a/Servers/WindowServer/WSMenuManager.cpp
+++ b/Servers/WindowServer/WSMenuManager.cpp
@@ -31,6 +31,15 @@ void WSMenuManager::setup()
     m_window->set_rect(WSWindowManager::the().menubar_rect());
 }
 
+bool WSMenuManager::is_open(const WSMenu& menu) const
+{
+    for (int i = 0; i < m_open_menu_stack.size(); ++i) {
+        if (&menu == m_open_menu_stack[i].ptr())
+            return true;
+    }
+    return false;
+}
+
 void WSMenuManager::draw()
 {
     auto& wm = WSWindowManager::the();
@@ -43,7 +52,7 @@ void WSMenuManager::draw()
     int index = 0;
     wm.for_each_active_menubar_menu([&](WSMenu& menu) {
         Color text_color = Color::Black;
-        if (&menu == wm.current_menu()) {
+        if (is_open(menu)) {
             painter.fill_rect(menu.rect_in_menubar(), Color::from_rgb(0xad714f));
             painter.draw_rect(menu.rect_in_menubar(), Color::from_rgb(0x793016));
             text_color = Color::White;
@@ -124,7 +133,9 @@ void WSMenuManager::event(CEvent& event)
 void WSMenuManager::handle_menu_mouse_event(WSMenu& menu, const WSMouseEvent& event)
 {
     auto& wm = WSWindowManager::the();
-    bool is_hover_with_any_menu_open = event.type() == WSMouseEvent::MouseMove && wm.current_menu() && (wm.current_menu()->menubar() || wm.current_menu() == wm.system_menu());
+    bool is_hover_with_any_menu_open = event.type() == WSMouseEvent::MouseMove
+                                       && !m_open_menu_stack.is_empty()
+                                       && (m_open_menu_stack.first()->menubar() || m_open_menu_stack.first() == wm.system_menu());
     bool is_mousedown_with_left_button = event.type() == WSMouseEvent::MouseDown && event.button() == MouseButton::Left;
     bool should_open_menu = &menu != wm.current_menu() && (is_hover_with_any_menu_open || is_mousedown_with_left_button);
 
diff --git a/Servers/WindowServer/WSMenuManager.h b/Servers/WindowServer/WSMenuManager.h
index d039ed4164..dab4717720 100644
--- a/Servers/WindowServer/WSMenuManager.h
+++ b/Servers/WindowServer/WSMenuManager.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "WSMenu.h"
 #include <LibCore/CObject.h>
 #include <WindowServer/WSCPUMonitor.h>
 #include <WindowServer/WSWindow.h>
@@ -15,6 +16,10 @@ public:
 
     virtual void event(CEvent&) override;
 
+    bool is_open(const WSMenu&) const;
+
+    Vector<WeakPtr<WSMenu>>& open_menu_stack() { return m_open_menu_stack; }
+
 private:
     WSWindow& window() { return *m_window; }
     const WSWindow& window() const { return *m_window; }
@@ -27,4 +32,6 @@ private:
     OwnPtr<WSWindow> m_window;
     WSCPUMonitor m_cpu_monitor;
     String m_username;
+
+    Vector<WeakPtr<WSMenu>> m_open_menu_stack;
 };
diff --git a/Servers/WindowServer/WSWindowManager.cpp b/Servers/WindowServer/WSWindowManager.cpp
index 04dcb9022a..56074469de 100644
--- a/Servers/WindowServer/WSWindowManager.cpp
+++ b/Servers/WindowServer/WSWindowManager.cpp
@@ -211,14 +211,22 @@ int WSWindowManager::menubar_menu_margin() const
     return 16;
 }
 
-void WSWindowManager::set_current_menu(WSMenu* menu)
+void WSWindowManager::set_current_menu(WSMenu* menu, bool is_submenu)
 {
     if (m_current_menu == menu)
         return;
-    if (m_current_menu)
+    if (!is_submenu && m_current_menu)
         m_current_menu->close();
     if (menu)
         m_current_menu = menu->make_weak_ptr();
+
+    if (!is_submenu) {
+        m_menu_manager.open_menu_stack().clear();
+        if (menu)
+            m_menu_manager.open_menu_stack().append(menu->make_weak_ptr());
+    } else {
+        m_menu_manager.open_menu_stack().append(menu->make_weak_ptr());
+    }
 }
 
 void WSWindowManager::set_current_menubar(WSMenuBar* menubar)
@@ -393,6 +401,11 @@ void WSWindowManager::close_current_menu()
     if (m_current_menu && m_current_menu->menu_window())
         m_current_menu->menu_window()->set_visible(false);
     m_current_menu = nullptr;
+    for (auto& menu : m_menu_manager.open_menu_stack()) {
+        if (menu)
+            menu->menu_window()->set_visible(false);
+    }
+    m_menu_manager.open_menu_stack().clear();
     m_menu_manager.refresh();
 }
 
@@ -696,6 +709,18 @@ void WSWindowManager::process_mouse_event(WSMouseEvent& event, WSWindow*& hovere
                 m_current_menu->clear_hovered_item();
             if (event.type() == WSEvent::MouseDown || event.type() == WSEvent::MouseUp)
                 close_current_menu();
+            if (event.type() == WSEvent::MouseMove) {
+                for (auto& menu : m_menu_manager.open_menu_stack()) {
+                    if (!menu)
+                        continue;
+                    if (!menu->menu_window()->rect().contains(event.position()))
+                        continue;
+                    hovered_window = menu->menu_window();
+                    auto translated_event = event.translated(-menu->menu_window()->position());
+                    deliver_mouse_event(*menu->menu_window(), translated_event);
+                    break;
+                }
+            }
         } else {
             hovered_window = &window;
             auto translated_event = event.translated(-window.position());
diff --git a/Servers/WindowServer/WSWindowManager.h b/Servers/WindowServer/WSWindowManager.h
index 3c0dabb072..cece8d2de2 100644
--- a/Servers/WindowServer/WSWindowManager.h
+++ b/Servers/WindowServer/WSWindowManager.h
@@ -78,11 +78,14 @@ public:
 
     void draw_window_switcher();
 
+    WSMenuManager& menu_manager() { return m_menu_manager; }
+    const WSMenuManager& menu_manager() const { return m_menu_manager; }
+
     Rect menubar_rect() const;
     WSMenuBar* current_menubar() { return m_current_menubar.ptr(); }
     void set_current_menubar(WSMenuBar*);
     WSMenu* current_menu() { return m_current_menu.ptr(); }
-    void set_current_menu(WSMenu*);
+    void set_current_menu(WSMenu*, bool is_submenu = false);
     WSMenu* system_menu() { return m_system_menu.ptr(); }
 
     const WSCursor& active_cursor() const;