diff --git a/autotests/client/test_wayland_subsurface.cpp b/autotests/client/test_wayland_subsurface.cpp
--- a/autotests/client/test_wayland_subsurface.cpp
+++ b/autotests/client/test_wayland_subsurface.cpp
@@ -54,6 +54,7 @@
     void testCast();
     void testSyncMode();
     void testDeSyncMode();
+    void testMainSurfaceFromTree();
 
 private:
     KWayland::Server::Display *m_display;
@@ -206,6 +207,7 @@
     QCOMPARE(serverSubSurface->parentSurface().data(), serverParentSurface);
     QCOMPARE(serverSubSurface->surface().data(), serverSurface);
     QCOMPARE(serverSurface->subSurface().data(), serverSubSurface);
+    QCOMPARE(serverSubSurface->mainSurface().data(), serverParentSurface);
     // children are only added after committing the surface
     QEXPECT_FAIL("", "Incorrect adding of child windows to workaround QtWayland behavior", Continue);
     QCOMPARE(serverParentSurface->childSubSurfaces().count(), 0);
@@ -695,5 +697,56 @@
     QCOMPARE(childSurface->buffer()->data(), image);
 }
 
+
+void TestSubSurface::testMainSurfaceFromTree()
+{
+    // this test verifies that in a tree of surfaces every surface has the same main surface
+    using namespace KWayland::Client;
+    using namespace KWayland::Server;
+    QSignalSpy surfaceCreatedSpy(m_compositorInterface, &CompositorInterface::surfaceCreated);
+    QVERIFY(surfaceCreatedSpy.isValid());
+
+    QScopedPointer<Surface> parentSurface(m_compositor->createSurface());
+    QVERIFY(surfaceCreatedSpy.wait());
+    auto parentServerSurface = surfaceCreatedSpy.last().first().value<SurfaceInterface*>();
+    QVERIFY(parentServerSurface);
+    QScopedPointer<Surface> childLevel1Surface(m_compositor->createSurface());
+    QVERIFY(surfaceCreatedSpy.wait());
+    auto childLevel1ServerSurface = surfaceCreatedSpy.last().first().value<SurfaceInterface*>();
+    QVERIFY(childLevel1ServerSurface);
+    QScopedPointer<Surface> childLevel2Surface(m_compositor->createSurface());
+    QVERIFY(surfaceCreatedSpy.wait());
+    auto childLevel2ServerSurface = surfaceCreatedSpy.last().first().value<SurfaceInterface*>();
+    QVERIFY(childLevel2ServerSurface);
+    QScopedPointer<Surface> childLevel3Surface(m_compositor->createSurface());
+    QVERIFY(surfaceCreatedSpy.wait());
+    auto childLevel3ServerSurface = surfaceCreatedSpy.last().first().value<SurfaceInterface*>();
+    QVERIFY(childLevel3ServerSurface);
+
+    QSignalSpy subSurfaceTreeChangedSpy(parentServerSurface, &SurfaceInterface::subSurfaceTreeChanged);
+    QVERIFY(subSurfaceTreeChangedSpy.isValid());
+
+    m_subCompositor->createSubSurface(childLevel1Surface.data(), parentSurface.data());
+    m_subCompositor->createSubSurface(childLevel2Surface.data(), childLevel1Surface.data());
+    m_subCompositor->createSubSurface(childLevel3Surface.data(), childLevel2Surface.data());
+
+    parentSurface->commit(Surface::CommitFlag::None);
+    QVERIFY(subSurfaceTreeChangedSpy.wait());
+
+    QCOMPARE(parentServerSurface->childSubSurfaces().count(), 1);
+    auto child = parentServerSurface->childSubSurfaces().first();
+    QCOMPARE(child->parentSurface().data(), parentServerSurface);
+    QCOMPARE(child->mainSurface().data(), parentServerSurface);
+    QCOMPARE(child->surface()->childSubSurfaces().count(), 1);
+    auto child2 = child->surface()->childSubSurfaces().first();
+    QCOMPARE(child2->parentSurface().data(), child->surface().data());
+    QCOMPARE(child2->mainSurface().data(), parentServerSurface);
+    QCOMPARE(child2->surface()->childSubSurfaces().count(), 1);
+    auto child3 = child2->surface()->childSubSurfaces().first();
+    QCOMPARE(child3->parentSurface().data(), child2->surface().data());
+    QCOMPARE(child3->mainSurface().data(), parentServerSurface);
+    QCOMPARE(child3->surface()->childSubSurfaces().count(), 0);
+}
+
 QTEST_GUILESS_MAIN(TestSubSurface)
 #include "test_wayland_subsurface.moc"
diff --git a/src/server/subcompositor_interface.h b/src/server/subcompositor_interface.h
--- a/src/server/subcompositor_interface.h
+++ b/src/server/subcompositor_interface.h
@@ -85,6 +85,12 @@
     QPointer<SurfaceInterface> surface();
     QPointer<SurfaceInterface> parentSurface();
 
+    /**
+     * @returns the main surface for the sub-surface tree, that is the first surface without a parent
+     * @since 5.7
+     **/
+    QPointer<SurfaceInterface> mainSurface() const;
+
 Q_SIGNALS:
     void positionChanged(const QPoint&);
     void modeChanged(KWayland::Server::SubSurfaceInterface::Mode);
diff --git a/src/server/subcompositor_interface.cpp b/src/server/subcompositor_interface.cpp
--- a/src/server/subcompositor_interface.cpp
+++ b/src/server/subcompositor_interface.cpp
@@ -329,6 +329,15 @@
     return false;
 }
 
+QPointer<SurfaceInterface> SubSurfaceInterface::mainSurface() const
+{
+    Q_D();
+    if (d->parent->d_func()->subSurface) {
+        return d->parent->d_func()->subSurface->mainSurface();
+    }
+    return d->parent;
+}
+
 SubSurfaceInterface::Private *SubSurfaceInterface::d_func() const
 {
     return reinterpret_cast<SubSurfaceInterface::Private*>(d.data());