diff --git a/CMakeLists.txt b/CMakeLists.txt
index bc338bc4..f827aa29 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -222,6 +222,15 @@ if (_GLFW_X11)
     list(APPEND glfw_LIBRARIES "${X11_Xrandr_LIB}")
     set(GLFW_PKG_DEPS "${GLFW_PKG_DEPS} xrandr")
 
+    # Check for Xinerama (legacy multi-monitor support)
+    if (NOT X11_Xinerama_FOUND)
+        message(FATAL_ERROR "The Xinerama library and headers were not found")
+    endif()
+
+    list(APPEND glfw_INCLUDE_DIRS "${X11_Xinerama_INCLUDE_PATH}")
+    list(APPEND glfw_LIBRARIES "${X11_Xinerama_LIB}")
+    set(GLFW_PKG_DEPS "${GLFW_PKG_DEPS} xinerama")
+
     # Check for XInput (high-resolution cursor motion)
     if (NOT X11_Xinput_FOUND)
         message(FATAL_ERROR "The XInput library and headers were not found")
diff --git a/src/x11_init.c b/src/x11_init.c
index 028d715d..ea0b6934 100644
--- a/src/x11_init.c
+++ b/src/x11_init.c
@@ -447,6 +447,8 @@ static void detectEWMH(void)
         getSupportedAtom(supportedAtoms, atomCount, "_NET_WM_STATE_ABOVE");
     _glfw.x11.NET_WM_STATE_FULLSCREEN =
         getSupportedAtom(supportedAtoms, atomCount, "_NET_WM_STATE_FULLSCREEN");
+    _glfw.x11.NET_WM_FULLSCREEN_MONITORS =
+        getSupportedAtom(supportedAtoms, atomCount, "_NET_WM_FULLSCREEN_MONITORS");
     _glfw.x11.NET_WM_NAME =
         getSupportedAtom(supportedAtoms, atomCount, "_NET_WM_NAME");
     _glfw.x11.NET_WM_ICON_NAME =
@@ -533,6 +535,14 @@ static GLboolean initExtensions(void)
         XRRFreeScreenResources(sr);
     }
 
+    if (XineramaQueryExtension(_glfw.x11.display,
+                               &_glfw.x11.xinerama.versionMajor,
+                               &_glfw.x11.xinerama.versionMinor))
+    {
+        if (XineramaIsActive(_glfw.x11.display))
+            _glfw.x11.xinerama.available = GL_TRUE;
+    }
+
     if (XQueryExtension(_glfw.x11.display,
                         "XInputExtension",
                         &_glfw.x11.xi.majorOpcode,
diff --git a/src/x11_monitor.c b/src/x11_monitor.c
index 679cafb0..d0bbb434 100644
--- a/src/x11_monitor.c
+++ b/src/x11_monitor.c
@@ -200,18 +200,23 @@ void _glfwRestoreVideoMode(_GLFWmonitor* monitor)
 
 _GLFWmonitor** _glfwPlatformGetMonitors(int* count)
 {
-    int i, j, size = 0, found = 0;
+    int i, j, k, size = 0, found = 0;
     _GLFWmonitor** monitors = NULL;
 
     *count = 0;
 
     if (_glfw.x11.randr.available)
     {
+        int screenCount = 0;
+        XineramaScreenInfo* screens = NULL;
         XRRScreenResources* sr = XRRGetScreenResources(_glfw.x11.display,
                                                        _glfw.x11.root);
         RROutput primary = XRRGetOutputPrimary(_glfw.x11.display,
                                                _glfw.x11.root);
 
+        if (_glfw.x11.xinerama.available)
+            screens = XineramaQueryScreens(_glfw.x11.display, &screenCount);
+
         for (i = 0;  i < sr->ncrtc;  i++)
         {
             XRRCrtcInfo* ci = XRRGetCrtcInfo(_glfw.x11.display,
@@ -240,6 +245,18 @@ _GLFWmonitor** _glfwPlatformGetMonitors(int* count)
                 monitors[found]->x11.output = ci->outputs[j];
                 monitors[found]->x11.crtc   = oi->crtc;
 
+                for (k = 0;  k < screenCount;  k++)
+                {
+                    if (screens[k].x_org == ci->x &&
+                        screens[k].y_org == ci->y &&
+                        screens[k].width == ci->width &&
+                        screens[k].height == ci->height)
+                    {
+                        monitors[found]->x11.index = k;
+                        break;
+                    }
+                }
+
                 XRRFreeOutputInfo(oi);
 
                 if (ci->outputs[j] == primary)
@@ -253,6 +270,9 @@ _GLFWmonitor** _glfwPlatformGetMonitors(int* count)
 
         XRRFreeScreenResources(sr);
 
+        if (screens)
+            XFree(screens);
+
         if (found == 0)
         {
             _glfwInputError(GLFW_PLATFORM_ERROR,
diff --git a/src/x11_platform.h b/src/x11_platform.h
index 7c4e72e2..a69705b3 100644
--- a/src/x11_platform.h
+++ b/src/x11_platform.h
@@ -48,6 +48,9 @@
 // The Xkb extension provides improved keyboard support
 #include <X11/XKBlib.h>
 
+// The Xinerama extension provides legacy monitor indices
+#include <X11/extensions/Xinerama.h>
+
 #include "posix_tls.h"
 
 #if defined(_GLFW_GLX)
@@ -130,6 +133,7 @@ typedef struct _GLFWlibraryX11
     Atom            NET_WM_STATE_ABOVE;
     Atom            NET_WM_STATE_FULLSCREEN;
     Atom            NET_WM_BYPASS_COMPOSITOR;
+    Atom            NET_WM_FULLSCREEN_MONITORS;
     Atom            NET_ACTIVE_WINDOW;
     Atom            NET_FRAME_EXTENTS;
     Atom            NET_REQUEST_FRAME_EXTENTS;
@@ -205,6 +209,12 @@ typedef struct _GLFWlibraryX11
         Window      source;
     } xdnd;
 
+    struct {
+        GLboolean   available;
+        int         versionMajor;
+        int         versionMinor;
+    } xinerama;
+
 } _GLFWlibraryX11;
 
 
@@ -216,6 +226,10 @@ typedef struct _GLFWmonitorX11
     RRCrtc          crtc;
     RRMode          oldMode;
 
+    // Index of corresponding Xinerama screen,
+    // for EWMH full screen window placement
+    int             index;
+
 } _GLFWmonitorX11;
 
 
diff --git a/src/x11_window.c b/src/x11_window.c
index ce3d8a66..dfc303fd 100644
--- a/src/x11_window.c
+++ b/src/x11_window.c
@@ -715,6 +715,27 @@ static void enterFullscreenMode(_GLFWwindow* window)
                         PropModeReplace, (unsigned char*) &value, 1);
     }
 
+    if (_glfw.x11.xinerama.available && _glfw.x11.NET_WM_FULLSCREEN_MONITORS)
+    {
+        XEvent event;
+        memset(&event, 0, sizeof(event));
+
+        event.type = ClientMessage;
+        event.xclient.window = window->x11.handle;
+        event.xclient.format = 32; // Data is 32-bit longs
+        event.xclient.message_type = _glfw.x11.NET_WM_FULLSCREEN_MONITORS;
+        event.xclient.data.l[0] = window->monitor->x11.index;
+        event.xclient.data.l[1] = window->monitor->x11.index;
+        event.xclient.data.l[2] = window->monitor->x11.index;
+        event.xclient.data.l[3] = window->monitor->x11.index;
+
+        XSendEvent(_glfw.x11.display,
+                   _glfw.x11.root,
+                   False,
+                   SubstructureNotifyMask | SubstructureRedirectMask,
+                   &event);
+    }
+
     if (_glfw.x11.NET_WM_STATE && _glfw.x11.NET_WM_STATE_FULLSCREEN)
     {
         int x, y;