diff --git a/3rdparty/QtPropertyBrowser/CMakeLists.txt b/3rdparty/QtPropertyBrowser/CMakeLists.txt
index a86b5c6b29..65101760e6 100644
--- a/3rdparty/QtPropertyBrowser/CMakeLists.txt
+++ b/3rdparty/QtPropertyBrowser/CMakeLists.txt
@@ -1,11 +1,3 @@
 CMAKE_MINIMUM_REQUIRED(VERSION 3.13)
-
 PROJECT(QtPropertyBrowser)
-
-##################### Look for required libraries ######################
-
-# Add QT dependencies
-FIND_PACKAGE(Qt5Widgets REQUIRED)
-
-######################### Add Primary Targets ##########################
 ADD_SUBDIRECTORY(src)
diff --git a/3rdparty/QtPropertyBrowser/src/CMakeLists.txt b/3rdparty/QtPropertyBrowser/src/CMakeLists.txt
index 9d02d58d12..ad67f6f7da 100644
--- a/3rdparty/QtPropertyBrowser/src/CMakeLists.txt
+++ b/3rdparty/QtPropertyBrowser/src/CMakeLists.txt
@@ -23,8 +23,13 @@ set(_RESOURCES
   qtpropertybrowser.qrc
   )
   
-QT5_WRAP_UI(_UI_SRCS ${_UI_FORMS})
-QT5_ADD_RESOURCES(_QRC_SRCS ${_RESOURCES})
+if (Qt6_FOUND)
+  QT6_WRAP_UI(_UI_SRCS ${_UI_FORMS})
+  QT6_ADD_RESOURCES(_QRC_SRCS ${_RESOURCES})
+else()
+  QT5_WRAP_UI(_UI_SRCS ${_UI_FORMS})
+  QT5_ADD_RESOURCES(_QRC_SRCS ${_RESOURCES})
+endif()
 
 set(TARGET_NAME ${PROJECT_NAME})
 
@@ -34,8 +39,14 @@ add_library(${TARGET_NAME} STATIC
   ${_QRC_SRCS}
   )
 
+target_compile_options(${TARGET_NAME} PRIVATE -Wno-deprecated-declarations)
+
 if (MSVC)
   target_compile_options(${TARGET_NAME} PRIVATE /wd4457 /wd4718)
 endif()
 
-target_link_libraries(${TARGET_NAME} Qt5::Widgets)
+if (Qt6_FOUND)
+  target_link_libraries(${TARGET_NAME} Qt6::Widgets)
+else()
+  target_link_libraries(${TARGET_NAME} Qt5::Widgets)
+endif()
diff --git a/3rdparty/QtPropertyBrowser/src/qt5compat.h b/3rdparty/QtPropertyBrowser/src/qt5compat.h
new file mode 100644
index 0000000000..969e74458c
--- /dev/null
+++ b/3rdparty/QtPropertyBrowser/src/qt5compat.h
@@ -0,0 +1,12 @@
+#pragma once
+#include <QtGlobal>
+
+#if QT_VERSION_MAJOR >= 6
+#include <QRegularExpression>
+#include <QRegularExpressionValidator>
+
+// QRegExp / QRegExpValidator aliases
+using QRegExp = QRegularExpression;
+using QRegExpValidator = QRegularExpressionValidator;
+
+#endif
diff --git a/3rdparty/QtPropertyBrowser/src/qteditorfactory.cpp b/3rdparty/QtPropertyBrowser/src/qteditorfactory.cpp
index 4920f472b3..d3a0b1ef1f 100644
--- a/3rdparty/QtPropertyBrowser/src/qteditorfactory.cpp
+++ b/3rdparty/QtPropertyBrowser/src/qteditorfactory.cpp
@@ -1545,7 +1545,11 @@ QtCharEdit::QtCharEdit(QWidget *parent)
 {
     QHBoxLayout *layout = new QHBoxLayout(this);
     layout->addWidget(m_lineEdit);
+#if QT_VERSION_MAJOR >= 6
+    layout->setContentsMargins(0,0,0,0);
+#else
     layout->setMargin(0);
+#endif
     m_lineEdit->installEventFilter(this);
     m_lineEdit->setReadOnly(true);
     m_lineEdit->setFocusProxy(this);
@@ -1669,7 +1673,13 @@ void QtCharEdit::keyReleaseEvent(QKeyEvent *e)
 void QtCharEdit::paintEvent(QPaintEvent *)
 {
     QStyleOption opt;
+#if QT_VERSION_MAJOR >= 6
+    opt.rect = this->rect();
+    opt.state = isEnabled() ? QStyle::State_Enabled : QStyle::State_None;
+    opt.palette = this->palette();
+#else
     opt.init(this);
+#endif
     QPainter p(this);
     style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
@@ -2240,7 +2250,13 @@ bool QtColorEditWidget::eventFilter(QObject *obj, QEvent *ev)
 void QtColorEditWidget::paintEvent(QPaintEvent *)
 {
     QStyleOption opt;
+#if QT_VERSION_MAJOR >= 6
+    opt.rect = this->rect();
+    opt.state = isEnabled() ? QStyle::State_Enabled : QStyle::State_None;
+    opt.palette = this->palette();
+#else
     opt.init(this);
+#endif
     QPainter p(this);
     style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
@@ -2462,7 +2478,13 @@ bool QtFontEditWidget::eventFilter(QObject *obj, QEvent *ev)
 void QtFontEditWidget::paintEvent(QPaintEvent *)
 {
     QStyleOption opt;
+#if QT_VERSION_MAJOR >= 6
+    opt.rect = this->rect();
+    opt.state = isEnabled() ? QStyle::State_Enabled : QStyle::State_None;
+    opt.palette = this->palette();
+#else
     opt.init(this);
+#endif
     QPainter p(this);
     style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
diff --git a/3rdparty/QtPropertyBrowser/src/qtpropertybrowser.h b/3rdparty/QtPropertyBrowser/src/qtpropertybrowser.h
index 1ca8783078..17e012cfdb 100644
--- a/3rdparty/QtPropertyBrowser/src/qtpropertybrowser.h
+++ b/3rdparty/QtPropertyBrowser/src/qtpropertybrowser.h
@@ -41,6 +41,8 @@
 #ifndef QTPROPERTYBROWSER_H
 #define QTPROPERTYBROWSER_H
 
+#include "qt5compat.h"
+
 #include <QWidget>
 #include <QtCore/QSet>
 
diff --git a/3rdparty/QtPropertyBrowser/src/qtpropertybrowserutils.cpp b/3rdparty/QtPropertyBrowser/src/qtpropertybrowserutils.cpp
index cd19583583..6f28fcd27b 100644
--- a/3rdparty/QtPropertyBrowser/src/qtpropertybrowserutils.cpp
+++ b/3rdparty/QtPropertyBrowser/src/qtpropertybrowserutils.cpp
@@ -262,7 +262,13 @@ void QtBoolEdit::mousePressEvent(QMouseEvent *event)
 void QtBoolEdit::paintEvent(QPaintEvent *)
 {
     QStyleOption opt;
+#if QT_VERSION_MAJOR >= 6
+    opt.rect = this->rect();
+    opt.state = isEnabled() ? QStyle::State_Enabled : QStyle::State_None;
+    opt.palette = this->palette();
+#else
     opt.init(this);
+#endif
     QPainter p(this);
     style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
@@ -274,7 +280,11 @@ QtKeySequenceEdit::QtKeySequenceEdit(QWidget *parent)
 {
     QHBoxLayout *layout = new QHBoxLayout(this);
     layout->addWidget(m_lineEdit);
+#if QT_VERSION_MAJOR >= 6
+    layout->setContentsMargins(0,0,0,0);
+#else
     layout->setMargin(0);
+#endif
     m_lineEdit->installEventFilter(this);
     m_lineEdit->setReadOnly(true);
     m_lineEdit->setFocusProxy(this);
@@ -408,7 +418,13 @@ void QtKeySequenceEdit::keyReleaseEvent(QKeyEvent *e)
 void QtKeySequenceEdit::paintEvent(QPaintEvent *)
 {
     QStyleOption opt;
+#if QT_VERSION_MAJOR >= 6
+    opt.rect = this->rect();
+    opt.state = isEnabled() ? QStyle::State_Enabled : QStyle::State_None;
+    opt.palette = this->palette();
+#else
     opt.init(this);
+#endif
     QPainter p(this);
     style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
diff --git a/3rdparty/QtPropertyBrowser/src/qtpropertymanager.cpp b/3rdparty/QtPropertyBrowser/src/qtpropertymanager.cpp
index ef627e9c28..2626af9383 100644
--- a/3rdparty/QtPropertyBrowser/src/qtpropertymanager.cpp
+++ b/3rdparty/QtPropertyBrowser/src/qtpropertymanager.cpp
@@ -1229,7 +1229,11 @@ class QtStringPropertyManagerPrivate
 
     struct Data
     {
-        Data() : regExp(QString(QLatin1Char('*')),  Qt::CaseSensitive, QRegExp::Wildcard)
+#if QT_VERSION_MAJOR >= 6
+        Data() : regExp(QRegularExpression(QStringLiteral(".*")))
+#else
+        Data() : regExp(QString(QLatin1Char('*')), Qt::CaseSensitive, QRegExp::Wildcard)
+#endif
         {
         }
         QString val;
@@ -1357,7 +1361,11 @@ void QtStringPropertyManager::setValue(QtProperty *property, const QString &val)
     if (data.val == val)
         return;
 
+#if QT_VERSION_MAJOR >= 6
+    if (data.regExp.isValid() && !data.regExp.match(val).hasMatch())
+#else
     if (data.regExp.isValid() && !data.regExp.exactMatch(val))
+#endif
         return;
 
     data.val = val;
@@ -5854,8 +5862,13 @@ void QtFontPropertyManager::setValue(QtProperty *property, const QFont &val)
         return;
 
     const QFont oldVal = it.value();
+#if QT_VERSION_MAJOR >= 6
+    if (oldVal == val && oldVal.resolve(val) == val)
+        return;
+#else
     if (oldVal == val && oldVal.resolve() == val.resolve())
         return;
+#endif
 
     it.value() = val;
 
diff --git a/3rdparty/QtPropertyBrowser/src/qttreepropertybrowser.cpp b/3rdparty/QtPropertyBrowser/src/qttreepropertybrowser.cpp
index 1ed0c98303..e1661e374a 100644
--- a/3rdparty/QtPropertyBrowser/src/qttreepropertybrowser.cpp
+++ b/3rdparty/QtPropertyBrowser/src/qttreepropertybrowser.cpp
@@ -132,9 +132,9 @@ class QtPropertyEditorView : public QTreeWidget
 protected:
     void mouseMoveEvent(QMouseEvent *event) override;
     void leaveEvent(QEvent *event) override;
-    void keyPressEvent(QKeyEvent *event) override;
-    void mousePressEvent(QMouseEvent *event) override;
-    void drawRow(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const override;
+    void keyPressEvent(QKeyEvent *event);
+    void mousePressEvent(QMouseEvent *event);
+    void drawRow(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const;
 
 Q_SIGNALS:
     void hoverPropertyChanged(QtBrowserItem *item);
@@ -160,7 +160,8 @@ void QtPropertyEditorView::drawRow(QPainter *painter, const QStyleOptionViewItem
             hasValue = property->hasValue();
     }
     if (!hasValue && m_editorPrivate->markPropertiesWithoutValue()) {
-        const QColor c = option.palette.color(QPalette::Dark);
+        QColor c = m_editorPrivate->calculatedBackgroundColor(m_editorPrivate->indexToBrowserItem(index));
+        if (!c.isValid()) c = option.palette.color(QPalette::Dark);
         painter->fillRect(option.rect, c);
         opt.palette.setColor(QPalette::AlternateBase, c);
     } else {
@@ -379,7 +380,8 @@ void QtPropertyEditorDelegate::paint(QPainter *painter, const QStyleOptionViewIt
     }
     QColor c;
     if (!hasValue && m_editorPrivate->markPropertiesWithoutValue()) {
-        c = opt.palette.color(QPalette::Dark);
+        c = m_editorPrivate->calculatedBackgroundColor(m_editorPrivate->indexToBrowserItem(index));
+        if (!c.isValid()) c = opt.palette.color(QPalette::Dark);
         opt.palette.setColor(QPalette::Text, opt.palette.color(QPalette::BrightText));
     } else {
         c = m_editorPrivate->calculatedBackgroundColor(m_editorPrivate->indexToBrowserItem(index));
@@ -486,7 +488,11 @@ static QIcon drawIndicatorIcon(const QPalette &palette, QStyle *style)
 void QtTreePropertyBrowserPrivate::init(QWidget *parent)
 {
     QHBoxLayout *layout = new QHBoxLayout(parent);
+#if QT_VERSION_MAJOR >= 6
+    layout->setContentsMargins(0,0,0,0);
+#else
     layout->setMargin(0);
+#endif
     m_treeWidget = new QtPropertyEditorView(parent);
     m_treeWidget->setEditorPrivate(this);
     m_treeWidget->setIconSize(QSize(18, 18));
@@ -610,7 +616,6 @@ void QtTreePropertyBrowserPrivate::propertyInserted(QtBrowserItem *index, QtBrow
 
     newItem->setFlags(newItem->flags() | Qt::ItemIsEditable);
     newItem->setExpanded(true);
-
     updateItem(newItem);
 }
 
diff --git a/3rdparty/QtPropertyBrowser/src/qtvariantproperty.cpp b/3rdparty/QtPropertyBrowser/src/qtvariantproperty.cpp
index c003f3e48e..a03f7a4261 100644
--- a/3rdparty/QtPropertyBrowser/src/qtvariantproperty.cpp
+++ b/3rdparty/QtPropertyBrowser/src/qtvariantproperty.cpp
@@ -986,8 +986,13 @@ QtVariantPropertyManager::QtVariantPropertyManager(QObject *parent)
     QtStringPropertyManager *stringPropertyManager = new QtStringPropertyManager(this);
     d_ptr->m_typeToPropertyManager[QVariant::String] = stringPropertyManager;
     d_ptr->m_typeToValueType[QVariant::String] = QVariant::String;
+#if QT_VERSION_MAJOR >= 6
+    d_ptr->m_typeToAttributeToAttributeType[QVariant::String][d_ptr->m_regExpAttribute] =
+            QMetaType::QRegularExpression; // int value for the type
+#else
     d_ptr->m_typeToAttributeToAttributeType[QVariant::String][d_ptr->m_regExpAttribute] =
             QVariant::RegExp;
+#endif
     connect(stringPropertyManager, SIGNAL(valueChanged(QtProperty *, const QString &)),
                 this, SLOT(slotValueChanged(QtProperty *, const QString &)));
     connect(stringPropertyManager, SIGNAL(regExpChanged(QtProperty *, const QRegExp &)),
diff --git a/3rdparty/python-console/CMakeLists.txt b/3rdparty/python-console/CMakeLists.txt
index 89433edc4d..b5c7975f86 100644
--- a/3rdparty/python-console/CMakeLists.txt
+++ b/3rdparty/python-console/CMakeLists.txt
@@ -2,7 +2,13 @@ cmake_minimum_required( VERSION 2.8 )
 project( PythonInterpreter )
 
 set(CMAKE_CXX_STANDARD 11)
-find_package(Qt5 COMPONENTS Core Widgets REQUIRED)
+find_package(Qt6 COMPONENTS Core Widgets REQUIRED)
+if (Qt6_FOUND)
+    message(STATUS "Using Qt6")
+else()
+    message(STATUS "Using Qt5")
+    find_package(Qt5 COMPONENTS Core Widgets REQUIRED)
+endif()
 
 find_package( PythonLibs REQUIRED )
 include_directories( ${PYTHON_INCLUDE_DIRS} )
@@ -10,7 +16,12 @@ include_directories( ${PYTHON_INCLUDE_DIRS} )
 add_executable( test_python_interpreter test_python_interpreter.cpp Interpreter.cpp )
 target_link_libraries( test_python_interpreter ${PYTHON_LIBRARIES} )
 
-qt5_wrap_cpp( Console_MOC Console.h )
+if (Qt6_FOUND)
+    qt6_wrap_cpp( Console_MOC Console.h )
+else()
+    qt5_wrap_cpp( Console_MOC Console.h )
+endif()
+
 add_executable( test_console test_console.cpp
     Console.cpp ${Console_MOC}
     ColumnFormatter.cpp
@@ -22,7 +33,12 @@ add_executable( test_console test_console.cpp
     ParseMessage.cpp
 )
 target_compile_definitions( test_console PRIVATE QT_NO_KEYWORDS)
-target_link_libraries( test_console Qt5::Widgets ${PYTHON_LIBRARIES} )
+
+if (Qt6_FOUND)
+    target_link_libraries( test_console Qt6::Widgets ${PYTHON_LIBRARIES} )
+else()
+    target_link_libraries( test_console Qt5::Widgets ${PYTHON_LIBRARIES} )
+endif()
 
 add_executable( test_parse_helper test_parse_helper.cpp 
     ParseHelper.cpp
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 562c718db0..9c4f3a1d80 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -197,8 +197,14 @@ else()
 endif()
 
 if (BUILD_GUI)
-    # Find the Qt5 libraries
-    find_package(Qt5 COMPONENTS Core Widgets OpenGL REQUIRED)
+    # Find the Qt6/5 libraries
+    find_package(Qt6 COMPONENTS Core Widgets OpenGL OpenGLWidgets QUIET)
+    if (Qt6_FOUND)
+        message(STATUS "Using Qt6")
+    else()
+        message(STATUS "Using Qt5")
+        find_package(Qt5 COMPONENTS Core Widgets OpenGL REQUIRED)
+    endif()
 
     # For higher quality backtraces
     set(CMAKE_ENABLE_EXPORTS ON)
diff --git a/gui/CMakeLists.txt b/gui/CMakeLists.txt
index ff5d92081a..d8b9f89790 100644
--- a/gui/CMakeLists.txt
+++ b/gui/CMakeLists.txt
@@ -27,10 +27,17 @@ set(GUI_SOURCES
     ${family}/mainwindow.h
 )
 
-qt5_add_resources(GUI_QT_RESOURCES
-    base.qrc
-    ${family}/nextpnr.qrc
-)
+if (Qt6_FOUND)
+    qt6_add_resources(GUI_QT_RESOURCES
+        base.qrc
+        ${family}/nextpnr.qrc
+    )
+else()
+    qt5_add_resources(GUI_QT_RESOURCES
+        base.qrc
+        ${family}/nextpnr.qrc
+    )
+endif()
 
 add_library(nextpnr-${target}-gui OBJECT
     ${GUI_SOURCES}
@@ -54,14 +61,17 @@ target_include_directories(nextpnr-${target}-gui PRIVATE
     ${CMAKE_SOURCE_DIR}/3rdparty/qtimgui
 )
 
-target_link_libraries(nextpnr-${target}-gui PUBLIC
-    Qt5::Widgets
-)
+if (Qt6_FOUND)
+    target_link_libraries(nextpnr-${target}-gui PUBLIC Qt6::Widgets)
+    target_link_libraries(nextpnr-${target}-gui PRIVATE Qt6::OpenGL Qt6::OpenGLWidgets)
+else()
+    target_link_libraries(nextpnr-${target}-gui PUBLIC Qt5::Widgets)
+    target_link_libraries(nextpnr-${target}-gui PRIVATE Qt5::OpenGL)
+endif()
 
 target_link_libraries(nextpnr-${target}-gui PRIVATE
     nextpnr-${target}-defs
     nextpnr_version
-    Qt5::OpenGL
     QtPropertyBrowser
     pybind11::headers
 )
diff --git a/gui/application.cc b/gui/application.cc
index b04d4a2f21..a558135638 100644
--- a/gui/application.cc
+++ b/gui/application.cc
@@ -96,6 +96,7 @@ Application::Application(int &argc, char **argv, bool noantialiasing) : QApplica
     QSurfaceFormat fmt;
     if (!noantialiasing)
         fmt.setSamples(10);
+    fmt.setRenderableType(QSurfaceFormat::OpenGL);
     fmt.setProfile(QSurfaceFormat::CoreProfile);
     // macOS is very picky about this version matching
     // the version of openGL  used in ImGuiRenderer
diff --git a/gui/designwidget.cc b/gui/designwidget.cc
index c14b7423d5..dfe110e323 100644
--- a/gui/designwidget.cc
+++ b/gui/designwidget.cc
@@ -20,6 +20,7 @@
 
 #include "designwidget.h"
 #include <QAction>
+#include <QActionGroup>
 #include <QApplication>
 #include <QGridLayout>
 #include <QLineEdit>
diff --git a/gui/fpgaviewwidget.cc b/gui/fpgaviewwidget.cc
index 3787536f30..aeb5ac88a8 100644
--- a/gui/fpgaviewwidget.cc
+++ b/gui/fpgaviewwidget.cc
@@ -22,7 +22,6 @@
 
 #include <QApplication>
 #include <QCoreApplication>
-#include <QDesktopWidget>
 #include <QDir>
 #include <QFileInfo>
 #include <QImageWriter>
@@ -36,6 +35,12 @@
 #include "log.h"
 #include "mainwindow.h"
 
+#if QT_VERSION_MAJOR >= 6
+#define EVENT_POS(event) ((event)->position())
+#else
+#define EVENT_POS(event) ((event)->pos())
+#endif
+
 NEXTPNR_NAMESPACE_BEGIN
 
 FPGAViewWidget::FPGAViewWidget(QWidget *parent)
@@ -728,7 +733,7 @@ void FPGAViewWidget::mousePressEvent(QMouseEvent *event)
         lastDragPos_ = event->pos();
     }
     if (btn_left && !shift) {
-        auto world = mouseToWorldCoordinates(event->x(), event->y());
+        auto world = mouseToWorldCoordinates(EVENT_POS(event).x(), EVENT_POS(event).y());
         auto closestOr = pickElement(world.x(), world.y());
         if (!closestOr) {
             // If we clicked on empty space and aren't holding down ctrl,
@@ -765,8 +770,8 @@ void FPGAViewWidget::mouseMoveEvent(QMouseEvent *event)
     bool btn_left = event->buttons() & Qt::LeftButton;
 
     if (btn_right || btn_mid || (btn_left && shift)) {
-        const int dx = event->x() - lastDragPos_.x();
-        const int dy = event->y() - lastDragPos_.y();
+        const int dx = EVENT_POS(event).x() - lastDragPos_.x();
+        const int dy = EVENT_POS(event).y() - lastDragPos_.y();
         lastDragPos_ = event->pos();
 
         auto world = mouseToWorldDimensions(dx, dy);
@@ -776,7 +781,7 @@ void FPGAViewWidget::mouseMoveEvent(QMouseEvent *event)
         return;
     }
 
-    auto world = mouseToWorldCoordinates(event->x(), event->y());
+    auto world = mouseToWorldCoordinates(EVENT_POS(event).x(), EVENT_POS(event).y());
     auto closestOr = pickElement(world.x(), world.y());
     // No elements? No decal.
     if (!closestOr) {
@@ -794,8 +799,8 @@ void FPGAViewWidget::mouseMoveEvent(QMouseEvent *event)
         QMutexLocker locked(&rendererArgsLock_);
         rendererArgs_->hoveredDecal = closest.decal(ctx_);
         rendererArgs_->changed = true;
-        rendererArgs_->x = event->x();
-        rendererArgs_->y = event->y();
+        rendererArgs_->x = EVENT_POS(event).x();
+        rendererArgs_->y = EVENT_POS(event).y();
         if (closest.type == ElementType::BEL) {
             rendererArgs_->hintText = std::string("BEL\n") + ctx_->getBelName(closest.bel).str(ctx_);
             CellInfo *cell = ctx_->getBoundBelCell(closest.bel);