diff --git a/autotests/mockclient.h b/autotests/mockclient.h
--- a/autotests/mockclient.h
+++ b/autotests/mockclient.h
@@ -52,12 +52,15 @@
     bool isShadeable() const override;
     bool isShaded() const override;
     QPalette palette() const override;
+    bool hasApplicationMenu() const override;
+    bool isApplicationMenuActive() const override;
     bool providesContextHelp() const override;
     void requestClose() override;
     void requestContextHelp() override;
     void requestToggleMaximization(Qt::MouseButtons buttons) override;
     void requestMinimize() override;
     void requestShowWindowMenu() override;
+    void requestShowApplicationMenu(const QRect &rect, int actionId) override;
     void requestToggleKeepAbove() override;
     void requestToggleKeepBelow() override;
     void requestToggleOnAllDesktops() override;
@@ -65,6 +68,8 @@
     int width() const override;
     WId windowId() const override;
 
+    void showApplicationMenu(int actionId) override;
+
     void setCloseable(bool set);
     void setMinimizable(bool set);
     void setProvidesContextHelp(bool set);
@@ -79,6 +84,7 @@
     void minimizeRequested();
     void quickHelpRequested();
     void menuRequested();
+    void applicationMenuRequested();
 
 private:
     bool m_closeable = false;
diff --git a/autotests/mockclient.cpp b/autotests/mockclient.cpp
--- a/autotests/mockclient.cpp
+++ b/autotests/mockclient.cpp
@@ -138,6 +138,16 @@
     return QPalette();
 }
 
+bool MockClient::hasApplicationMenu() const
+{
+    return false; // FIXME TODO
+}
+
+bool MockClient::isApplicationMenuActive() const
+{
+    return false;
+}
+
 bool MockClient::providesContextHelp() const
 {
     return m_contextHelp;
@@ -191,6 +201,13 @@
     emit menuRequested();
 }
 
+void MockClient::requestShowApplicationMenu(const QRect &rect, int actionId)
+{
+    Q_UNUSED(rect);
+    Q_UNUSED(actionId);
+    emit applicationMenuRequested(); // FIXME TODO pass geometry
+}
+
 void MockClient::requestToggleKeepAbove()
 {
     m_keepAbove = !m_keepAbove;
@@ -266,3 +283,8 @@
     m_height = h;
     emit client()->heightChanged(h);
 }
+
+void MockClient::showApplicationMenu(int actionId)
+{
+    Q_UNUSED(actionId)
+}
diff --git a/src/decoratedclient.h b/src/decoratedclient.h
--- a/src/decoratedclient.h
+++ b/src/decoratedclient.h
@@ -168,6 +168,12 @@
      **/
     Q_PROPERTY(Qt::Edges adjacentScreenEdges READ adjacentScreenEdges NOTIFY adjacentScreenEdgesChanged)
 
+    // FIXME TODO docs @since
+    Q_PROPERTY(bool hasApplicationMenu READ hasApplicationMenu NOTIFY hasApplicationMenuChanged)
+
+    // FIXME TODO docs @since
+    Q_PROPERTY(bool applicationMenuActive READ isApplicationMenuActive NOTIFY applicationMenuActiveChanged)
+
     // TODO: properties for windowId and decorationId?
 
 public:
@@ -221,6 +227,24 @@
      **/
     QColor color(ColorGroup group, ColorRole role) const;
 
+    /**
+     * Whether the DecoratedClient has an application menu
+     *
+     * @since 5.9
+     */
+    bool hasApplicationMenu() const;
+    /**
+     * Whether the application menu of this DecoratedClient is currently shown to the user
+     * @since 5.9
+     */
+    bool isApplicationMenuActive() const;
+
+    /**
+     * Request the application menu to be shown to the user
+     * @param actionId The DBus menu ID of the action that should be highlighted, 0 for none.
+     */
+    void showApplicationMenu(int actionId);
+
 Q_SIGNALS:
     void activeChanged(bool);
     void captionChanged(QString);
@@ -247,6 +271,9 @@
     void paletteChanged(const QPalette &palette);
     void adjacentScreenEdgesChanged(Qt::Edges edges);
 
+    void hasApplicationMenuChanged(bool);
+    void applicationMenuActiveChanged(bool);
+
 private:
     friend class Decoration;
     DecoratedClient(Decoration *parent, DecorationBridge *bridge);
diff --git a/src/decoratedclient.cpp b/src/decoratedclient.cpp
--- a/src/decoratedclient.cpp
+++ b/src/decoratedclient.cpp
@@ -66,6 +66,8 @@
 DELEGATE(int, height)
 DELEGATE(QPalette, palette)
 DELEGATE(Qt::Edges, adjacentScreenEdges)
+DELEGATE(bool, hasApplicationMenu)
+DELEGATE(bool, isApplicationMenuActive)
 
 #undef DELEGATE
 
@@ -84,4 +86,9 @@
     return d->color(group, role);
 }
 
+void DecoratedClient::showApplicationMenu(int actionId)
+{
+    d->showApplicationMenu(actionId);
+}
+
 } // namespace
diff --git a/src/decoration.h b/src/decoration.h
--- a/src/decoration.h
+++ b/src/decoration.h
@@ -177,6 +177,9 @@
     void requestToggleKeepBelow();
     void requestShowWindowMenu();
 
+    void showApplicationMenu(int actionId);
+    void requestShowApplicationMenu(const QRect &rect, int actionId);
+
     void update(const QRect &rect);
     void update();
 
diff --git a/src/decoration.cpp b/src/decoration.cpp
--- a/src/decoration.cpp
+++ b/src/decoration.cpp
@@ -185,6 +185,22 @@
     d->client->d->requestToggleMaximization(buttons);
 }
 
+void Decoration::showApplicationMenu(int actionId)
+{
+    auto it = std::find_if(d->buttons.constBegin(), d->buttons.constEnd(), [](DecorationButton *button) {
+        return button->type() == DecorationButtonType::ApplicationMenu;
+    });
+
+    if (it != d->buttons.constEnd()) {
+        requestShowApplicationMenu((*it)->geometry().toRect(), actionId);
+    }
+}
+
+void Decoration::requestShowApplicationMenu(const QRect &rect, int actionId)
+{
+    d->client->d->requestShowApplicationMenu(rect, actionId);
+}
+
 #define DELEGATE(name, variableName, type, emitValue) \
 void Decoration::name(type a) \
 { \
diff --git a/src/decorationbutton.cpp b/src/decorationbutton.cpp
--- a/src/decorationbutton.cpp
+++ b/src/decorationbutton.cpp
@@ -77,6 +77,16 @@
         setPressAndHold(settings->isCloseOnDoubleClickOnMenu());
         setAcceptedButtons(Qt::LeftButton | Qt::RightButton);
         break;
+    case DecorationButtonType::ApplicationMenu:
+        setVisible(c->hasApplicationMenu());
+        setCheckable(true); // will be "checked" whilst the menu is opened
+        // FIXME TODO connect directly and figure out the button geometry/offset stuff
+        QObject::connect(q, &DecorationButton::clicked, decoration.data(), [this] {
+            decoration->requestShowApplicationMenu(q->geometry().toRect(), 0 /* actionId */);
+        }, Qt::QueuedConnection); //&Decoration::requestShowApplicationMenu, Qt::QueuedConnection);
+        QObject::connect(c, &DecoratedClient::hasApplicationMenuChanged, q, &DecorationButton::setVisible);
+        QObject::connect(c, &DecoratedClient::applicationMenuActiveChanged, q, &DecorationButton::setChecked);
+        break;
     case DecorationButtonType::OnAllDesktops:
         setVisible(settings->isOnAllDesktopsAvailable());
         setCheckable(true);
diff --git a/src/private/decoratedclientprivate.h b/src/private/decoratedclientprivate.h
--- a/src/private/decoratedclientprivate.h
+++ b/src/private/decoratedclientprivate.h
@@ -76,6 +76,9 @@
     virtual QPalette palette() const = 0;
     virtual Qt::Edges adjacentScreenEdges() const = 0;
 
+    virtual bool hasApplicationMenu() const = 0;
+    virtual bool isApplicationMenuActive() const = 0;
+
     virtual void requestClose() = 0;
     virtual void requestToggleMaximization(Qt::MouseButtons buttons) = 0;
     virtual void requestMinimize() = 0;
@@ -86,6 +89,9 @@
     virtual void requestToggleKeepBelow() = 0;
     virtual void requestShowWindowMenu() = 0;
 
+    virtual void showApplicationMenu(int actionId) = 0;
+    virtual void requestShowApplicationMenu(const QRect &rect, int actionId) = 0;
+
     Decoration *decoration();
     Decoration *decoration() const;