diff --git a/.travis.yml b/.travis.yml
index 721c0be7d..613c74357 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -52,14 +52,17 @@ addons:
     sources:
       # sources list: https://github.com/travis-ci/apt-source-safelist/blob/master/ubuntu.json
       - sourceline: 'ppa:qbittorrent-team/qbittorrent-stable'
+      - sourceline: 'ppa:beineri/opt-qt59-xenial'
     packages:
       # packages list: https://github.com/travis-ci/apt-package-safelist/blob/master/ubuntu-trusty
       - [autoconf, automake, colormake]
       - [libboost-dev, libboost-system-dev]
       - libssl-dev
       - libtorrent-rasterbar-dev
-      - [qtbase5-dev, qttools5-dev-tools, libqt5svg5-dev]
+      - [qt59base, qt59svg, qt59tools]
       - zlib1g-dev
+      # required for Qt 5.9 from 'beineri' PPA
+      - libgl1-mesa-dev
   homebrew:
     update: true
     packages:
@@ -85,6 +88,11 @@ before_install:
     if [ "$TRAVIS_OS_NAME" = "linux" ]; then
       # setup virtual display for after_success target
       if [ "$gui" = "true" ]; then export "DISPLAY=:99.0" && /sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1280x1024x16 ; fi ;
+      
+      # Qt 5.9
+      PATH=/opt/qt59/bin:${PATH}
+      qmake_conf="$qmake_conf PKG_CONFIG_PATH=/opt/qt59/lib/pkgconfig:$PKG_CONFIG_PATH"
+      cmake_conf="$cmake_conf PKG_CONFIG_PATH=/opt/qt59/lib/pkgconfig:$PKG_CONFIG_PATH"
     fi
   - |
     if [ "$TRAVIS_OS_NAME" = "osx" ]; then
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 86b2fdd46..924e8ccd0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -31,7 +31,7 @@ include(FeatureSummary)
 
 # version requirements
 set(requiredBoostVersion 1.35)
-set(requiredQtVersion 5.5.1)
+set(requiredQtVersion 5.9.0)
 set(requiredOpensslVersion 1.0)
 set(requiredLibtorrentVersion 1.1.10)
 
diff --git a/INSTALL b/INSTALL
index 9d7434658..d5ad61289 100644
--- a/INSTALL
+++ b/INSTALL
@@ -11,7 +11,7 @@ qBittorrent - A BitTorrent client in C++ / Qt
 
   - OpenSSL >= 1.0
 
-  - Qt >= 5.5.1
+  - Qt >= 5.9.0
 
   - zlib >= 1.2.5.2
 
diff --git a/configure b/configure
index 166855440..4bfc0af21 100755
--- a/configure
+++ b/configure
@@ -1431,7 +1431,7 @@ Some influential environment variables:
               directories to add to pkg-config's search path
   PKG_CONFIG_LIBDIR
               path overriding pkg-config's built-in search path
-  QT_QMAKE    value of host_bins for Qt5Core >= 5.5.1, overriding pkg-config
+  QT_QMAKE    value of host_bins for Qt5Core >= 5.9.0, overriding pkg-config
   Qt5Svg_CFLAGS
               C compiler flags for Qt5Svg, overriding pkg-config
   Qt5Svg_LIBS linker flags for Qt5Svg, overriding pkg-config
@@ -4498,8 +4498,8 @@ $as_echo "$enable_webui" >&6; }
 esac
 
 if test -n "$PKG_CONFIG" && \
-    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"Qt5Core >= 5.5.1\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "Qt5Core >= 5.5.1") 2>&5
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"Qt5Core >= 5.9.0\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "Qt5Core >= 5.9.0") 2>&5
   ac_status=$?
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
@@ -4508,12 +4508,12 @@ if test -n "$QT_QMAKE"; then
     pkg_cv_QT_QMAKE="$QT_QMAKE"
  elif test -n "$PKG_CONFIG"; then
     if test -n "$PKG_CONFIG" && \
-    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"Qt5Core >= 5.5.1\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "Qt5Core >= 5.5.1") 2>&5
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"Qt5Core >= 5.9.0\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "Qt5Core >= 5.9.0") 2>&5
   ac_status=$?
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
-  pkg_cv_QT_QMAKE=`$PKG_CONFIG --variable="host_bins" "Qt5Core >= 5.5.1" 2>/dev/null`
+  pkg_cv_QT_QMAKE=`$PKG_CONFIG --variable="host_bins" "Qt5Core >= 5.9.0" 2>/dev/null`
 		      test "x$?" != "x0" && pkg_failed=yes
 else
   pkg_failed=yes
@@ -4540,8 +4540,8 @@ fi
 
 fi
 
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for Qt5 qmake >= 5.5.1" >&5
-$as_echo_n "checking for Qt5 qmake >= 5.5.1... " >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for Qt5 qmake >= 5.9.0" >&5
+$as_echo_n "checking for Qt5 qmake >= 5.9.0... " >&6; }
 if test "x$QT_QMAKE" != "x"; then :
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: $QT_QMAKE" >&5
 $as_echo "$QT_QMAKE" >&6; }
@@ -4655,11 +4655,11 @@ case "x$enable_qt_dbus" in #(
   "xyes") :
     { $as_echo "$as_me:${as_lineno-$LINENO}: result: yes" >&5
 $as_echo "yes" >&6; }
-               { $as_echo "$as_me:${as_lineno-$LINENO}: checking for Qt5DBus >= 5.5.1" >&5
-$as_echo_n "checking for Qt5DBus >= 5.5.1... " >&6; }
+               { $as_echo "$as_me:${as_lineno-$LINENO}: checking for Qt5DBus >= 5.9.0" >&5
+$as_echo_n "checking for Qt5DBus >= 5.9.0... " >&6; }
        if test -n "$PKG_CONFIG" && \
-    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"Qt5DBus >= 5.5.1\""; } >&5
-  ($PKG_CONFIG --exists --print-errors "Qt5DBus >= 5.5.1") 2>&5
+    { { $as_echo "$as_me:${as_lineno-$LINENO}: \$PKG_CONFIG --exists --print-errors \"Qt5DBus >= 5.9.0\""; } >&5
+  ($PKG_CONFIG --exists --print-errors "Qt5DBus >= 5.9.0") 2>&5
   ac_status=$?
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; then
diff --git a/m4/qbittorrent.m4 b/m4/qbittorrent.m4
index 7ef4a227a..1dff738af 100644
--- a/m4/qbittorrent.m4
+++ b/m4/qbittorrent.m4
@@ -5,9 +5,9 @@
 # Sets the QT_QMAKE variable to the path of Qt5 qmake if found.
 # --------------------------------------
 AC_DEFUN([FIND_QT5],
-[PKG_CHECK_EXISTS([Qt5Core >= 5.5.1],
+[PKG_CHECK_EXISTS([Qt5Core >= 5.9.0],
                  [PKG_CHECK_VAR(QT_QMAKE,
-                                [Qt5Core >= 5.5.1],
+                                [Qt5Core >= 5.9.0],
                                 [host_bins])
                  ])
 
@@ -18,7 +18,7 @@ AS_IF([test -f "$QT_QMAKE/qmake"],
                              [QT_QMAKE=""])
               ])
 
-AC_MSG_CHECKING([for Qt5 qmake >= 5.5.1])
+AC_MSG_CHECKING([for Qt5 qmake >= 5.9.0])
 AS_IF([test "x$QT_QMAKE" != "x"],
       [AC_MSG_RESULT([$QT_QMAKE])],
       [AC_MSG_RESULT([not found])]
@@ -29,8 +29,8 @@ AS_IF([test "x$QT_QMAKE" != "x"],
 # Sets the HAVE_QTDBUS variable to true or false.
 # --------------------------------------
 AC_DEFUN([FIND_QTDBUS],
-       [AC_MSG_CHECKING([for Qt5DBus >= 5.5.1])
-       PKG_CHECK_EXISTS([Qt5DBus >= 5.5.1],
+       [AC_MSG_CHECKING([for Qt5DBus >= 5.9.0])
+       PKG_CHECK_EXISTS([Qt5DBus >= 5.9.0],
                         [AC_MSG_RESULT([found])
                          HAVE_QTDBUS=[true]],
                         [AC_MSG_RESULT([not found])
diff --git a/src/app/application.cpp b/src/app/application.cpp
index 207dec302..4dd1e3020 100644
--- a/src/app/application.cpp
+++ b/src/app/application.cpp
@@ -147,10 +147,8 @@ Application::Application(const QString &id, int &argc, char **argv)
 #if !defined(DISABLE_GUI)
     setAttribute(Qt::AA_UseHighDpiPixmaps, true);  // opt-in to the high DPI pixmap support
     setQuitOnLastWindowClosed(false);
-#if QT_VERSION >= QT_VERSION_CHECK(5, 7, 0)
     setDesktopFileName("org.qbittorrent.qBittorrent");
 #endif
-#endif
 
 #if defined(Q_OS_WIN) && !defined(DISABLE_GUI)
     connect(this, &QGuiApplication::commitDataRequest, this, &Application::shutdownCleanup, Qt::DirectConnection);
diff --git a/src/base/bittorrent/session.cpp b/src/base/bittorrent/session.cpp
index 95d5d2708..829c82a9e 100644
--- a/src/base/bittorrent/session.cpp
+++ b/src/base/bittorrent/session.cpp
@@ -2179,16 +2179,7 @@ void Session::networkConfigurationChange(const QNetworkConfiguration &cfg)
 
     const QString changedInterface = cfg.name();
 
-    // workaround for QTBUG-52633: check interface IPs, react only if the IPs have changed
-    // seems to be present only with NetworkManager, hence Q_OS_LINUX
-#if defined Q_OS_LINUX && QT_VERSION >= QT_VERSION_CHECK(5, 0, 0) && QT_VERSION < QT_VERSION_CHECK(5, 7, 1)
-    static QStringList boundIPs = getListeningIPs();
-    const QStringList newBoundIPs = getListeningIPs();
-    if ((configuredInterfaceName == changedInterface) && (boundIPs != newBoundIPs)) {
-        boundIPs = newBoundIPs;
-#else
     if (configuredInterfaceName == changedInterface) {
-#endif
         Logger::instance()->addMessage(tr("Network configuration of %1 has changed, refreshing session binding", "e.g: Network configuration of tun0 has changed, refreshing session binding").arg(changedInterface), Log::INFO);
         configureListeningInterface();
     }
diff --git a/src/base/net/reverseresolution.cpp b/src/base/net/reverseresolution.cpp
index 68c075baa..116de9ef0 100644
--- a/src/base/net/reverseresolution.cpp
+++ b/src/base/net/reverseresolution.cpp
@@ -62,11 +62,7 @@ void ReverseResolution::resolve(const QString &ip)
     }
     else {
         // Actually resolve the ip
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 9, 0))
         m_lookups.insert(QHostInfo::lookupHost(ip, this, &ReverseResolution::hostResolved), ip);
-#else
-        m_lookups.insert(QHostInfo::lookupHost(ip, this, SLOT(hostResolved(QHostInfo))), ip);
-#endif
     }
 }
 
diff --git a/src/base/search/searchhandler.cpp b/src/base/search/searchhandler.cpp
index 5cb820628..f0dcb4c55 100644
--- a/src/base/search/searchhandler.cpp
+++ b/src/base/search/searchhandler.cpp
@@ -74,12 +74,7 @@ SearchHandler::SearchHandler(const QString &pattern, const QString &category, co
     m_searchProcess->setProgram(Utils::ForeignApps::pythonInfo().executableName);
     m_searchProcess->setArguments(params + m_pattern.split(' '));
 
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
     connect(m_searchProcess, &QProcess::errorOccurred, this, &SearchHandler::processFailed);
-#else
-    connect(m_searchProcess, static_cast<void (QProcess::*)(QProcess::ProcessError)>(&QProcess::error)
-            , this, &SearchHandler::processFailed);
-#endif
     connect(m_searchProcess, &QProcess::readyReadStandardOutput, this, &SearchHandler::readSearchOutput);
     connect(m_searchProcess, static_cast<void (QProcess::*)(int)>(&QProcess::finished)
             , this, &SearchHandler::processFinished);
diff --git a/src/gui/utils.cpp b/src/gui/utils.cpp
index 9151284a1..6a53920f3 100644
--- a/src/gui/utils.cpp
+++ b/src/gui/utils.cpp
@@ -55,11 +55,7 @@ qreal Utils::Gui::screenScalingFactor(const QWidget *widget)
 #elif defined(Q_OS_MAC)
     return 1;
 #else
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
     return widget->devicePixelRatioF();
-#else
-    return widget->devicePixelRatio();
-#endif
 #endif // Q_OS_WIN
 }
 
diff --git a/src/webui/webapplication.cpp b/src/webui/webapplication.cpp
index 0caa27fc7..53e69b2f6 100644
--- a/src/webui/webapplication.cpp
+++ b/src/webui/webapplication.cpp
@@ -630,19 +630,7 @@ bool WebApplication::validateHostHeader(const QStringList &domains) const
     }
 
     // try matching host header with local address
-#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
     const bool sameAddr = m_env.localAddress.isEqual(QHostAddress(requestHost));
-#else
-    const auto equal = [](const Q_IPV6ADDR &l, const Q_IPV6ADDR &r) -> bool
-    {
-        for (int i = 0; i < 16; ++i) {
-            if (l[i] != r[i])
-                return false;
-        }
-        return true;
-    };
-    const bool sameAddr = equal(m_env.localAddress.toIPv6Address(), QHostAddress(requestHost).toIPv6Address());
-#endif
 
     if (sameAddr)
         return true;