diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1a38c247e..16485caab 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,7 +29,7 @@ set(CMAKE_AUTOMOC ON)
 set(CMAKE_AUTOUIC ON)
 set(CMAKE_AUTORCC ON)
 
-set(REQUIRED_QT_VERSION "5.12")
+set(REQUIRED_QT_VERSION "5.15.0")
 set(KF5_MINIMUM_VERSION "5.36.0")
 set(LXQT_GLOBALKEYS_MINIMUM_VERSION "0.17.0")
 set(LXQT_MINIMUM_VERSION "0.17.0")
diff --git a/panel/config/addplugindialog.cpp b/panel/config/addplugindialog.cpp
index cb0899a23..5c461f474 100644
--- a/panel/config/addplugindialog.cpp
+++ b/panel/config/addplugindialog.cpp
@@ -49,11 +49,7 @@ AddPluginDialog::AddPluginDialog(QWidget *parent):
     ui->setupUi(this);
 
     QStringList desktopFilesDirs;
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     desktopFilesDirs << QString::fromLocal8Bit(qgetenv("LXQT_PANEL_PLUGINS_DIR")).split(QLatin1Char(':'), Qt::SkipEmptyParts);
-#else
-    desktopFilesDirs << QString::fromLocal8Bit(qgetenv("LXQT_PANEL_PLUGINS_DIR")).split(QLatin1Char(':'), QString::SkipEmptyParts);
-#endif
     desktopFilesDirs << QStringLiteral("%1/%2").arg(XdgDirs::dataHome(), QStringLiteral("/lxqt/lxqt-panel"));
     desktopFilesDirs << QStringLiteral(PLUGIN_DESKTOPS_DIR);
 
diff --git a/panel/lxqtpanel.cpp b/panel/lxqtpanel.cpp
index 324c4460d..1598c5efa 100644
--- a/panel/lxqtpanel.cpp
+++ b/panel/lxqtpanel.cpp
@@ -430,11 +430,7 @@ void LXQtPanel::show()
 QStringList pluginDesktopDirs()
 {
     QStringList dirs;
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     dirs << QString::fromLocal8Bit(qgetenv("LXQT_PANEL_PLUGINS_DIR")).split(QLatin1Char(':'), Qt::SkipEmptyParts);
-#else
-    dirs << QString::fromLocal8Bit(qgetenv("LXQT_PANEL_PLUGINS_DIR")).split(QLatin1Char(':'), QString::SkipEmptyParts);
-#endif
     dirs << QStringLiteral("%1/%2").arg(XdgDirs::dataHome(), QStringLiteral("/lxqt/lxqt-panel"));
     dirs << QStringLiteral(PLUGIN_DESKTOPS_DIR);
     return dirs;
@@ -1127,11 +1123,7 @@ bool LXQtPanel::event(QEvent *event)
         // Sometimes Qt needs to re-create the underlying window of the widget and
         // the winId() may be changed at runtime. So we need to reset all X11 properties
         // when this happens.
-        #if (QT_VERSION >= QT_VERSION_CHECK(5,14,0))
             qDebug() << "WinIdChange" << Qt::hex << effectiveWinId() << "handle" << windowHandle() << windowHandle()->screen();
-        #else
-            qDebug() << "WinIdChange" << hex << effectiveWinId() << "handle" << windowHandle() << windowHandle()->screen();
-        #endif
 
         // Qt::WA_X11NetWmWindowTypeDock becomes ineffective in Qt 5
         // See QTBUG-39887: https://bugreports.qt-project.org/browse/QTBUG-39887
diff --git a/panel/panelpluginsmodel.cpp b/panel/panelpluginsmodel.cpp
index a614656bf..40d015fcf 100644
--- a/panel/panelpluginsmodel.cpp
+++ b/panel/panelpluginsmodel.cpp
@@ -319,11 +319,7 @@ void PanelPluginsModel::onMovePluginUp(QModelIndex const & index)
         return; //can't move up
 
     beginMoveRows(QModelIndex(), row, row, QModelIndex(), row - 1);
-#if (QT_VERSION >= QT_VERSION_CHECK(5,13,0))
     mPlugins.swapItemsAt(row - 1, row);
-#else
-    mPlugins.swap(row - 1, row);
-#endif
     endMoveRows();
     pluginslist_t::const_reference moved_plugin = mPlugins[row - 1];
     pluginslist_t::const_reference prev_plugin = mPlugins[row];
@@ -346,11 +342,7 @@ void PanelPluginsModel::onMovePluginDown(QModelIndex const & index)
         return; //can't move down
 
     beginMoveRows(QModelIndex(), row, row, QModelIndex(), row + 2);
-#if (QT_VERSION >= QT_VERSION_CHECK(5,13,0))
     mPlugins.swapItemsAt(row, row + 1);
-#else
-    mPlugins.swap(row, row + 1);
-#endif
     endMoveRows();
     pluginslist_t::const_reference moved_plugin = mPlugins[row + 1];
     pluginslist_t::const_reference next_plugin = mPlugins[row];
diff --git a/plugin-desktopswitch/desktopswitch.cpp b/plugin-desktopswitch/desktopswitch.cpp
index e1a70523c..13a050929 100644
--- a/plugin-desktopswitch/desktopswitch.cpp
+++ b/plugin-desktopswitch/desktopswitch.cpp
@@ -54,11 +54,7 @@ DesktopSwitch::DesktopSwitch(const ILXQtPanelPluginStartupInfo &startupInfo) :
 {
     m_buttons = new QButtonGroup(this);
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     connect (m_pSignalMapper, &QSignalMapper::mappedInt, this, &DesktopSwitch::setDesktop);
-#else
-    connect (m_pSignalMapper, QOverload<int>::of(&QSignalMapper::mapped), this, &DesktopSwitch::setDesktop);
-#endif
 
 
     mLayout = new LXQt::GridLayout(&mWidget);
@@ -69,14 +65,7 @@ DesktopSwitch::DesktopSwitch(const ILXQtPanelPluginStartupInfo &startupInfo) :
     onCurrentDesktopChanged(KWindowSystem::currentDesktop());
     QTimer::singleShot(0, this, SLOT(registerShortcuts()));
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     connect(m_buttons, &QButtonGroup::idClicked, this, &DesktopSwitch::setDesktop);
-#else
-    connect(m_buttons, QOverload<QAbstractButton *>::of(&QButtonGroup::buttonClicked), this, [=](QAbstractButton * /*button*/){
-        int id = m_buttons->checkedId();
-        setDesktop(id);
-    });
-#endif
 
     connect(KWindowSystem::self(), &KWindowSystem::numberOfDesktopsChanged, this, &DesktopSwitch::onNumberOfDesktopsChanged);
     connect(KWindowSystem::self(), &KWindowSystem::currentDesktopChanged,   this, &DesktopSwitch::onCurrentDesktopChanged);
diff --git a/plugin-directorymenu/directorymenu.cpp b/plugin-directorymenu/directorymenu.cpp
index 79f068daa..494abd4c5 100644
--- a/plugin-directorymenu/directorymenu.cpp
+++ b/plugin-directorymenu/directorymenu.cpp
@@ -54,16 +54,9 @@ DirectoryMenu::DirectoryMenu(const ILXQtPanelPluginStartupInfo &startupInfo) :
 
     connect(&mButton, &QToolButton::clicked, this, &DirectoryMenu::showMenu);
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     connect(mOpenDirectorySignalMapper, &QSignalMapper::mappedString, this, &DirectoryMenu::openDirectory);
     connect(mOpenTerminalSignalMapper,  &QSignalMapper::mappedString, this, &DirectoryMenu::openInTerminal);
     connect(mMenuSignalMapper,          &QSignalMapper::mappedString, this, &DirectoryMenu::addMenu);
-#else
-    connect(&mButton, SIGNAL(clicked()), this, SLOT(showMenu()));
-    connect(mOpenDirectorySignalMapper, SIGNAL(mapped(QString)), this, SLOT(openDirectory(QString)));
-    connect(mOpenTerminalSignalMapper, SIGNAL(mapped(QString)), this, SLOT(openInTerminal(QString)));
-    connect(mMenuSignalMapper, SIGNAL(mapped(QString)), this, SLOT(addMenu(QString)));
-#endif
 
     settingsChanged();
 }
@@ -131,19 +124,11 @@ void DirectoryMenu::addActions(QMenu* menu, const QString& path)
     mPathStrings.push_back(path);
 
     QAction* openDirectoryAction = menu->addAction(XdgIcon::fromTheme(QStringLiteral("folder")), tr("Open"));
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     connect(openDirectoryAction, &QAction::triggered, mOpenDirectorySignalMapper, [this] { mOpenDirectorySignalMapper->map(); } );
-#else
-    connect(openDirectoryAction, SIGNAL(triggered()), mOpenDirectorySignalMapper, SLOT(map()));
-#endif
     mOpenDirectorySignalMapper->setMapping(openDirectoryAction, mPathStrings.back());
 
     QAction* openTerminalAction = menu->addAction(XdgIcon::fromTheme(QStringLiteral("folder")), tr("Open in terminal"));
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     connect(openTerminalAction, &QAction::triggered, mOpenTerminalSignalMapper, [this] { mOpenTerminalSignalMapper->map(); } );
-#else
-    connect(openTerminalAction, SIGNAL(triggered()), mOpenTerminalSignalMapper, SLOT(map()));
-#endif
     mOpenTerminalSignalMapper->setMapping(openTerminalAction, mPathStrings.back());
 
     menu->addSeparator();
@@ -159,11 +144,7 @@ void DirectoryMenu::addActions(QMenu* menu, const QString& path)
 
             QMenu* subMenu = menu->addMenu(XdgIcon::fromTheme(QStringLiteral("folder")), mPathStrings.back());
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
             connect(subMenu, &QMenu::aboutToShow, mMenuSignalMapper, [this] { mMenuSignalMapper->map(); } );
-#else
-            connect(subMenu, SIGNAL(aboutToShow()), mMenuSignalMapper, SLOT(map()));
-#endif
             mMenuSignalMapper->setMapping(subMenu, entry.absoluteFilePath());
         }
     }
diff --git a/plugin-quicklaunch/lxqtquicklaunch.cpp b/plugin-quicklaunch/lxqtquicklaunch.cpp
index d325a6dc8..c3f2ce81d 100644
--- a/plugin-quicklaunch/lxqtquicklaunch.cpp
+++ b/plugin-quicklaunch/lxqtquicklaunch.cpp
@@ -198,13 +198,8 @@ void LXQtQuickLaunch::dropEvent(QDropEvent *e)
         return;
     }
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5,14,0))
     const auto & urls = e->mimeData()->urls();
     for (const QUrl &url : QSet<QUrl>{urls.cbegin(), urls.cend()})
-#else
-    const auto urls = e->mimeData()->urls().toSet();
-    for (const QUrl &url : urls)
-#endif
     {
         QString fileName(url.isLocalFile() ? url.toLocalFile() : url.url());
         QFileInfo fi(fileName);
diff --git a/plugin-quicklaunch/quicklaunchaction.cpp b/plugin-quicklaunch/quicklaunchaction.cpp
index 830b67cb7..fc445f64f 100644
--- a/plugin-quicklaunch/quicklaunchaction.cpp
+++ b/plugin-quicklaunch/quicklaunchaction.cpp
@@ -123,12 +123,8 @@ void QuickLaunchAction::execAction(QString additionalAction)
     {
         case ActionLegacy:
         {
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
             QStringList args = QProcess::splitCommand(exec);
             QProcess::startDetached(args.takeFirst(), args);
-#else
-            QProcess::startDetached(exec);
-#endif
             break;
         }
         case ActionXdg:
diff --git a/plugin-statusnotifier/statusnotifierbutton.h b/plugin-statusnotifier/statusnotifierbutton.h
index 3a14213a0..7f0f45f68 100644
--- a/plugin-statusnotifier/statusnotifierbutton.h
+++ b/plugin-statusnotifier/statusnotifierbutton.h
@@ -38,16 +38,6 @@
 #include <QMenu>
 #include <QTimer>
 
-#if QT_VERSION < QT_VERSION_CHECK(5, 5, 0)
-template <typename T> inline T qFromUnaligned(const uchar *src)
-{
-    T dest;
-    const size_t size = sizeof(T);
-    memcpy(&dest, src, size);
-    return dest;
-}
-#endif
-
 class ILXQtPanelPlugin;
 class SniAsync;
 
diff --git a/plugin-sysstat/lxqtsysstatcolours.cpp b/plugin-sysstat/lxqtsysstatcolours.cpp
index d9dad17dd..6a46fd20a 100644
--- a/plugin-sysstat/lxqtsysstatcolours.cpp
+++ b/plugin-sysstat/lxqtsysstatcolours.cpp
@@ -80,11 +80,7 @@ LXQtSysStatColours::LXQtSysStatColours(QWidget *parent) :
         ++iterator;
     }
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     connect(mSelectColourMapper, &QSignalMapper::mappedString, this, &LXQtSysStatColours::selectColour);
-#else
-    connect(mSelectColourMapper, QOverload<const QString &>::of(&QSignalMapper::mapped), this, &LXQtSysStatColours::selectColour);
-#endif
 }
 
 LXQtSysStatColours::~LXQtSysStatColours()
diff --git a/plugin-taskbar/lxqttaskbar.cpp b/plugin-taskbar/lxqttaskbar.cpp
index 8e04ec001..aa4abe580 100644
--- a/plugin-taskbar/lxqttaskbar.cpp
+++ b/plugin-taskbar/lxqttaskbar.cpp
@@ -90,11 +90,7 @@ LXQtTaskBar::LXQtTaskBar(ILXQtPanelPlugin *plugin, QWidget *parent) :
     QTimer::singleShot(0, this, &LXQtTaskBar::settingsChanged);
     setAcceptDrops(true);
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
     connect(mSignalMapper, &QSignalMapper::mappedInt, this, &LXQtTaskBar::activateTask);
-#else
-    connect(mSignalMapper, static_cast<void (QSignalMapper::*)(int)>(&QSignalMapper::mapped), this, &LXQtTaskBar::activateTask);
-#endif
     QTimer::singleShot(0, this, &LXQtTaskBar::registerShortcuts);
 
     connect(KWindowSystem::self(), static_cast<void (KWindowSystem::*)(WId, NET::Properties, NET::Properties2)>(&KWindowSystem::windowChanged)
diff --git a/plugin-taskbar/lxqttaskbutton.cpp b/plugin-taskbar/lxqttaskbutton.cpp
index c8660f707..ad11c544c 100644
--- a/plugin-taskbar/lxqttaskbutton.cpp
+++ b/plugin-taskbar/lxqttaskbutton.cpp
@@ -147,11 +147,7 @@ void LXQtTaskButton::updateIcon()
     }
     if (ico.isNull())
     {
-#if QT_VERSION >= 0x050600
         int devicePixels = mIconSize * devicePixelRatioF();
-#else
-        int devicePixels = mIconSize * devicePixelRatio();
-#endif
         ico = KWindowSystem::icon(mWindow, devicePixels, devicePixels);
     }
     setIcon(ico.isNull() ? XdgIcon::defaultApplicationIcon() : ico);
diff --git a/plugin-volume/alsaengine.cpp b/plugin-volume/alsaengine.cpp
index 15db0506e..a0bdff521 100644
--- a/plugin-volume/alsaengine.cpp
+++ b/plugin-volume/alsaengine.cpp
@@ -178,11 +178,7 @@ void AlsaEngine::discoverDevices()
             struct pollfd pfd;
             if (snd_mixer_poll_descriptors(mixer, &pfd, 1)) {
                 QSocketNotifier *notifier = new QSocketNotifier(pfd.fd, QSocketNotifier::Read, this);
-            #if (QT_VERSION >= QT_VERSION_CHECK(5,15,0))
                 connect(notifier, &QSocketNotifier::activated, this, [this] (QSocketDescriptor socket, QSocketNotifier::Type) { this->driveAlsaEventHandling(socket); });
-            #else
-                connect(notifier, SIGNAL(activated(int)), this, SLOT(driveAlsaEventHandling(int)));
-            #endif
                 m_mixerMap.insert(pfd.fd, mixer);
             }