diff --git a/CMakeLists.txt b/CMakeLists.txt
index 94ef43fcb4..d9f98bf23e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1232,12 +1232,17 @@ status("")
 status("  GUI: ")
 
 if(WITH_QT OR HAVE_QT)
-  if(HAVE_QT5)
-    status("    QT:" "YES (ver ${Qt5Core_VERSION_STRING})")
-    status("      QT OpenGL support:" HAVE_QT_OPENGL THEN "YES (${Qt5OpenGL_LIBRARIES} ${Qt5OpenGL_VERSION_STRING})" ELSE NO)
-  elseif(HAVE_QT)
+  if(HAVE_QT)
     status("    QT:" "YES (ver ${QT_VERSION_MAJOR}.${QT_VERSION_MINOR}.${QT_VERSION_PATCH} ${QT_EDITION})")
-    status("      QT OpenGL support:" HAVE_QT_OPENGL THEN "YES (${QT_QTOPENGL_LIBRARY})" ELSE NO)
+    if(HAVE_QT_OPENGL)
+      if(Qt${QT_VERSION_MAJOR}OpenGL_LIBRARIES)
+        status("      QT OpenGL support:" HAVE_QT_OPENGL THEN "YES (${Qt${QT_VERSION_MAJOR}OpenGL_LIBRARIES} ${Qt${QT_VERSION_MAJOR}OpenGL_VERSION_STRING})" ELSE NO)
+      else()
+        status("      QT OpenGL support:" HAVE_QT_OPENGL THEN "YES (${QT_QTOPENGL_LIBRARY})" ELSE NO)
+      endif()
+    else()
+      status("      QT OpenGL support:" "NO")
+    endif()
   else()
     status("    QT:" "NO")
   endif()
diff --git a/cmake/OpenCVDetectVTK.cmake b/cmake/OpenCVDetectVTK.cmake
index 14956886e3..94ab735592 100644
--- a/cmake/OpenCVDetectVTK.cmake
+++ b/cmake/OpenCVDetectVTK.cmake
@@ -26,31 +26,14 @@ if(VTK_VERSION VERSION_LESS "5.8.0")
 endif()
 
 # Different Qt versions can't be linked together
-if(HAVE_QT5 AND VTK_VERSION VERSION_LESS "6.0.0")
-  if(VTK_USE_QT)
-    message(STATUS "VTK support is disabled. Incompatible combination: OpenCV + Qt5 and VTK ver.${VTK_VERSION} + Qt4")
-  endif()
-endif()
-
-# Different Qt versions can't be linked together. VTK 6.0.0 doesn't provide a way to get Qt version it was linked with
-if(HAVE_QT5 AND VTK_VERSION VERSION_EQUAL "6.0.0" AND NOT DEFINED FORCE_VTK)
-  message(STATUS "VTK support is disabled. Possible incompatible combination: OpenCV+Qt5, and VTK ver.${VTK_VERSION} with Qt4")
-  message(STATUS "If it is known that VTK was compiled without Qt4, please define '-DFORCE_VTK=TRUE' flag in CMake")
+if((HAVE_QT AND VTK_USE_QT)
+    AND NOT DEFINED FORCE_VTK  # deprecated
+    AND NOT DEFINED OPENCV_FORCE_VTK
+)
+  message(STATUS "VTK support is disabled. Possible incompatible combination: OpenCV+Qt, and VTK ver.${VTK_VERSION} with Qt")
+  message(STATUS "If it is known that VTK was compiled without Qt4, please define '-DOPENCV_FORCE_VTK=TRUE' flag in CMake")
   return()
 endif()
 
-# Different Qt versions can't be linked together
-if(HAVE_QT AND VTK_VERSION VERSION_GREATER "6.0.0" AND NOT ${VTK_QT_VERSION} STREQUAL "")
-  if(HAVE_QT5 AND ${VTK_QT_VERSION} EQUAL "4")
-    message(STATUS "VTK support is disabled. Incompatible combination: OpenCV + Qt5 and VTK ver.${VTK_VERSION} + Qt4")
-    return()
-  endif()
-
-  if(NOT HAVE_QT5 AND ${VTK_QT_VERSION} EQUAL "5")
-    message(STATUS "VTK support is disabled. Incompatible combination: OpenCV + Qt4 and VTK ver.${VTK_VERSION} + Qt5")
-    return()
-  endif()
-endif()
-
 set(HAVE_VTK ON)
 message(STATUS "Found VTK ${VTK_VERSION} (${VTK_USE_FILE})")
diff --git a/cmake/OpenCVFindLibsGUI.cmake b/cmake/OpenCVFindLibsGUI.cmake
index 82f7e0ff12..5e7db6c199 100644
--- a/cmake/OpenCVFindLibsGUI.cmake
+++ b/cmake/OpenCVFindLibsGUI.cmake
@@ -11,25 +11,50 @@ if(WITH_WIN32UI)
     CMAKE_FLAGS "-DLINK_LIBRARIES:STRING=user32;gdi32")
 endif()
 
-# --- QT4 ---
-ocv_clear_vars(HAVE_QT HAVE_QT5)
-if(WITH_QT)
-  if(NOT WITH_QT EQUAL 4)
-    find_package(Qt5 COMPONENTS Core Gui Widgets Test Concurrent REQUIRED NO_MODULE)
-    if(Qt5_FOUND)
-      set(HAVE_QT5 ON)
-      set(HAVE_QT  ON)
-      find_package(Qt5 COMPONENTS OpenGL QUIET)
-      if(Qt5OpenGL_FOUND)
-        set(QT_QTOPENGL_FOUND ON)
-      endif()
-    endif()
+macro(ocv_find_package_Qt4)
+  find_package(Qt4 COMPONENTS QtCore QtGui QtTest ${ARGN})
+  if(QT4_FOUND)
+    set(QT_FOUND 1)
+    ocv_assert(QT_VERSION_MAJOR EQUAL 4)
   endif()
+endmacro()
 
-  if(NOT HAVE_QT)
-    find_package(Qt4 REQUIRED QtCore QtGui QtTest)
-    if(QT4_FOUND)
-      set(HAVE_QT TRUE)
+macro(ocv_find_package_Qt OCV_QT_VER)
+  find_package(Qt${OCV_QT_VER} COMPONENTS Core Gui Widgets Test Concurrent ${ARGN} NO_MODULE)
+  if(Qt${OCV_QT_VER}_FOUND)
+    set(QT_FOUND 1)
+    set(QT_VERSION "${Qt${OCV_QT_VER}_VERSION}")
+    set(QT_VERSION_MAJOR "${Qt${OCV_QT_VER}_VERSION_MAJOR}")
+    set(QT_VERSION_MINOR "${Qt${OCV_QT_VER}_VERSION_MINOR}")
+    set(QT_VERSION_PATCH "${Qt${OCV_QT_VER}_VERSION_PATCH}")
+    set(QT_VERSION_TWEAK "${Qt${OCV_QT_VER}_VERSION_TWEAK}")
+    set(QT_VERSION_COUNT "${Qt${OCV_QT_VER}_VERSION_COUNT}")
+  endif()
+endmacro()
+
+# --- QT4 ---
+if(WITH_QT)
+  if(NOT WITH_QT GREATER 0)
+    # BUG: Qt5Config.cmake script can't handle components properly: find_package(QT NAMES Qt6 Qt5 REQUIRED NO_MODULE COMPONENTS Core Gui Widgets Test Concurrent)
+    ocv_find_package_Qt(6 QUIET)
+    if(NOT QT_FOUND)
+      ocv_find_package_Qt(5 QUIET)
+    endif()
+    if(NOT QT_FOUND)
+      ocv_find_package_Qt4(QUIET)
+    endif()
+  elseif(WITH_QT EQUAL 4)
+    ocv_find_package_Qt4(REQUIRED)
+  else()  # WITH_QT=<major version>
+    ocv_find_package_Qt("${WITH_QT}" REQUIRED)
+  endif()
+  if(QT_FOUND)
+    set(HAVE_QT ON)
+    if(QT_VERSION_MAJOR GREATER 4)
+      find_package(Qt${QT_VERSION_MAJOR} COMPONENTS OpenGL QUIET)
+      if(Qt${QT_VERSION_MAJOR}OpenGL_FOUND)
+        set(QT_QTOPENGL_FOUND ON)  # HAVE_QT_OPENGL is defined below
+      endif()
     endif()
   endif()
 endif()
diff --git a/modules/highgui/CMakeLists.txt b/modules/highgui/CMakeLists.txt
index 296f4cab2b..6e69961099 100644
--- a/modules/highgui/CMakeLists.txt
+++ b/modules/highgui/CMakeLists.txt
@@ -41,46 +41,55 @@ file(GLOB highgui_ext_hdrs
 # Removing WinRT API headers by default
 list(REMOVE_ITEM highgui_ext_hdrs "${CMAKE_CURRENT_LIST_DIR}/include/opencv2/${name}/highgui_winrt.hpp")
 
-if(HAVE_QT5)
-  # "Automoc" doesn't work properly with opencv_world build, use QT5_WRAP_CPP() directly
-  #set(CMAKE_AUTOMOC ON)
+if(HAVE_QT)
+  if(QT_VERSION_MAJOR GREATER 4)
+    # "Automoc" doesn't work properly with opencv_world build, use QT<ver>_WRAP_CPP() directly
+    #set(CMAKE_AUTOMOC ON)
 
-  set(CMAKE_INCLUDE_CURRENT_DIR ON)
+    set(CMAKE_INCLUDE_CURRENT_DIR ON)
 
-  QT5_ADD_RESOURCES(_RCC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.qrc)
-  QT5_WRAP_CPP(_MOC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h)
-  list(APPEND highgui_srcs
-       ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.cpp
-       ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h
-       ${_MOC_OUTFILES}
-       ${_RCC_OUTFILES})
+    if(QT_VERSION_MAJOR EQUAL 6)
+      QT6_ADD_RESOURCES(_RCC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.qrc)
+      QT6_WRAP_CPP(_MOC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h)
+    elseif(QT_VERSION_MAJOR EQUAL 5)
+      QT5_ADD_RESOURCES(_RCC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.qrc)
+      QT5_WRAP_CPP(_MOC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h)
+    else()
+      message(FATAL_ERROR "Unsuported QT version: ${QT_VERSION_MAJOR}")
+    endif()
 
-  foreach(dt5_dep Core Gui Widgets Test Concurrent)
-    add_definitions(${Qt5${dt5_dep}_DEFINITIONS})
-    include_directories(${Qt5${dt5_dep}_INCLUDE_DIRS})
-    list(APPEND HIGHGUI_LIBRARIES ${Qt5${dt5_dep}_LIBRARIES})
-  endforeach()
+    list(APPEND highgui_srcs
+         ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.cpp
+         ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h
+         ${_MOC_OUTFILES}
+         ${_RCC_OUTFILES})
 
-  if(HAVE_QT_OPENGL)
-    add_definitions(${Qt5OpenGL_DEFINITIONS})
-    include_directories(${Qt5OpenGL_INCLUDE_DIRS})
-    list(APPEND HIGHGUI_LIBRARIES ${Qt5OpenGL_LIBRARIES})
-  endif()
+    set(qt_deps Core Gui Widgets Test Concurrent)
+    if(HAVE_QT_OPENGL)
+      list(APPEND qt_deps OpenGL)
+    endif()
 
-elseif(HAVE_QT)
-  if (HAVE_QT_OPENGL)
-    set(QT_USE_QTOPENGL TRUE)
-  endif()
-  include(${QT_USE_FILE})
+    foreach(dt_dep ${qt_deps})
+      add_definitions(${Qt${QT_VERSION_MAJOR}${dt_dep}_DEFINITIONS})
+      include_directories(${Qt${QT_VERSION_MAJOR}${dt_dep}_INCLUDE_DIRS})
+      list(APPEND HIGHGUI_LIBRARIES ${Qt${QT_VERSION_MAJOR}${dt_dep}_LIBRARIES})
+    endforeach()
+  else()
+    ocv_assert(QT_VERSION_MAJOR EQUAL 4)
+    if (HAVE_QT_OPENGL)
+      set(QT_USE_QTOPENGL TRUE)
+    endif()
+    include(${QT_USE_FILE})
 
-  QT4_ADD_RESOURCES(_RCC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.qrc)
-  QT4_WRAP_CPP(_MOC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h)
+    QT4_ADD_RESOURCES(_RCC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.qrc)
+    QT4_WRAP_CPP(_MOC_OUTFILES ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.h)
 
-  list(APPEND HIGHGUI_LIBRARIES ${QT_LIBRARIES})
-  list(APPEND highgui_srcs ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.cpp ${_MOC_OUTFILES} ${_RCC_OUTFILES})
-  ocv_check_flag_support(CXX -Wno-missing-declarations _have_flag "")
-  if(${_have_flag})
-    set_source_files_properties(${_RCC_OUTFILES} PROPERTIES COMPILE_FLAGS -Wno-missing-declarations)
+    list(APPEND HIGHGUI_LIBRARIES ${QT_LIBRARIES})
+    list(APPEND highgui_srcs ${CMAKE_CURRENT_LIST_DIR}/src/window_QT.cpp ${_MOC_OUTFILES} ${_RCC_OUTFILES})
+    ocv_check_flag_support(CXX -Wno-missing-declarations _have_flag "")
+    if(${_have_flag})
+      set_source_files_properties(${_RCC_OUTFILES} PROPERTIES COMPILE_FLAGS -Wno-missing-declarations)
+    endif()
   endif()
 elseif(WINRT)
   if(NOT WINRT_8_0)
diff --git a/modules/highgui/src/window_QT.cpp b/modules/highgui/src/window_QT.cpp
index 8dff03117e..e7ee43cf5e 100644
--- a/modules/highgui/src/window_QT.cpp
+++ b/modules/highgui/src/window_QT.cpp
@@ -64,6 +64,38 @@
 #endif
 
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 15, 0)
+#define Qt_MiddleButton Qt::MiddleButton
+inline Qt::Orientation wheelEventOrientation(QWheelEvent *we) {
+    if (std::abs(we->angleDelta().x()) < std::abs(we->angleDelta().y()))
+        return Qt::Vertical;
+    else
+        return Qt::Horizontal;
+}
+inline int wheelEventDelta(QWheelEvent *we) {
+    if(wheelEventOrientation(we) == Qt::Vertical)
+        return we->angleDelta().y();
+    else
+        return we->angleDelta().x();
+}
+inline QPoint wheelEventPos(QWheelEvent *we) {
+    return we->position().toPoint();
+}
+#else
+#define Qt_MiddleButton Qt::MidButton
+inline Qt::Orientation wheelEventOrientation(QWheelEvent *we) {
+    return we->orientation();
+}
+inline int wheelEventDelta(QWheelEvent *we) {
+    return we->delta();
+}
+inline QPoint wheelEventPos(QWheelEvent *we) {
+    return we->pos();
+}
+
+#endif
+
+
 //Static and global first
 static GuiReceiver *guiMainThread = NULL;
 static int parameterSystemC = 1;
@@ -1579,7 +1611,9 @@ CvWinProperties::CvWinProperties(QString name_paraWindow, QObject* /*parent*/)
     myLayout->setObjectName(QString::fromUtf8("boxLayout"));
     myLayout->setContentsMargins(0, 0, 0, 0);
     myLayout->setSpacing(0);
+#if QT_VERSION < QT_VERSION_CHECK(5, 13, 0)
     myLayout->setMargin(0);
+#endif
     myLayout->setSizeConstraint(QLayout::SetFixedSize);
     setLayout(myLayout);
 
@@ -1957,7 +1991,9 @@ void CvWindow::createBarLayout()
     myBarLayout->setObjectName(QString::fromUtf8("barLayout"));
     myBarLayout->setContentsMargins(0, 0, 0, 0);
     myBarLayout->setSpacing(0);
+#if QT_VERSION < QT_VERSION_CHECK(5, 13, 0)
     myBarLayout->setMargin(0);
+#endif
 }
 
 
@@ -1967,7 +2003,9 @@ void CvWindow::createGlobalLayout()
     myGlobalLayout->setObjectName(QString::fromUtf8("boxLayout"));
     myGlobalLayout->setContentsMargins(0, 0, 0, 0);
     myGlobalLayout->setSpacing(0);
+#if QT_VERSION < QT_VERSION_CHECK(5, 13, 0)
     myGlobalLayout->setMargin(0);
+#endif
     setMinimumSize(1, 1);
 
     if (param_flags == CV_WINDOW_AUTOSIZE)
@@ -2205,7 +2243,7 @@ void CvWindow::icvLoadControlPanel()
             }
             if (t->type == type_CvButtonbar)
             {
-                int subsize = settings.beginReadArray(QString("buttonbar")+i);
+                int subsize = settings.beginReadArray(QString("buttonbar%1").arg(i));
 
                 if ( subsize == ((CvButtonbar*)t)->layout()->count() )
                     icvLoadButtonbar((CvButtonbar*)t,&settings);
@@ -2236,7 +2274,7 @@ void CvWindow::icvSaveControlPanel()
         }
         if (t->type == type_CvButtonbar)
         {
-            settings.beginWriteArray(QString("buttonbar")+i);
+            settings.beginWriteArray(QString("buttonbar%1").arg(i));
             icvSaveButtonbar((CvButtonbar*)t,&settings);
             settings.endArray();
         }
@@ -2396,14 +2434,14 @@ void OCVViewPort::icvmouseHandler(QMouseEvent* evnt, type_mouse_event category,
         flags |= CV_EVENT_FLAG_LBUTTON;
     if(buttons & Qt::RightButton)
         flags |= CV_EVENT_FLAG_RBUTTON;
-    if(buttons & Qt::MidButton)
+    if(buttons & Qt_MiddleButton)
         flags |= CV_EVENT_FLAG_MBUTTON;
 
     if (cv_event == -1) {
         if (category == mouse_wheel) {
             QWheelEvent *we = (QWheelEvent *) evnt;
-            cv_event = ((we->orientation() == Qt::Vertical) ? CV_EVENT_MOUSEWHEEL : CV_EVENT_MOUSEHWHEEL);
-            flags |= (we->delta() & 0xffff)<<16;
+            cv_event = ((wheelEventOrientation(we) == Qt::Vertical) ? CV_EVENT_MOUSEWHEEL : CV_EVENT_MOUSEHWHEEL);
+            flags |= (wheelEventDelta(we) & 0xffff)<<16;
             return;
         }
         switch(evnt->button())
@@ -2416,7 +2454,7 @@ void OCVViewPort::icvmouseHandler(QMouseEvent* evnt, type_mouse_event category,
             cv_event = tableMouseButtons[category][1];
             flags |= CV_EVENT_FLAG_RBUTTON;
             break;
-        case Qt::MidButton:
+        case Qt_MiddleButton:
             cv_event = tableMouseButtons[category][2];
             flags |= CV_EVENT_FLAG_MBUTTON;
             break;
@@ -2772,7 +2810,7 @@ void DefaultViewPort::wheelEvent(QWheelEvent* evnt)
 {
     icvmouseEvent((QMouseEvent *)evnt, mouse_wheel);
 
-    scaleView(evnt->delta() / 240.0, evnt->pos());
+    scaleView(wheelEventDelta(evnt) / 240.0, wheelEventPos(evnt));
     viewport()->update();
 
     QWidget::wheelEvent(evnt);