diff --git a/src/apprt/gtk/App.zig b/src/apprt/gtk/App.zig
index cc7dac1c4..ef299e31f 100644
--- a/src/apprt/gtk/App.zig
+++ b/src/apprt/gtk/App.zig
@@ -156,6 +156,35 @@ pub fn init(core_app: *CoreApp, opts: Options) !App {
         return error.GtkApplicationRegisterFailed;
     }
 
+    const display = c.gdk_display_get_default();
+    if (c.g_type_check_instance_is_a(@ptrCast(@alignCast(display)), c.gdk_x11_display_get_type()) != 0) {
+        // Set the X11 window class property (WM_CLASS) if are are on an X11
+        // display.
+        //
+        // Note that we also set the program name here using g_set_prgname.
+        // This is how the instance name field for WM_CLASS is derived when
+        // calling gdk_x11_display_set_program_class; there does not seem to be
+        // a way to set it directly. It does not look like this is being set by
+        // our other app initialization routines currently, but since we're
+        // currently deriving its value from x11-instance-name effectively, I
+        // feel like gating it behind an X11 check is better intent.
+        //
+        // This makes the property show up like so when using xprop:
+        //
+        //     WM_CLASS(STRING) = "ghostty", "com.mitchellh.ghostty"
+        //
+        // Append "-debug" on both when using the debug build.
+        //
+        const prgname = if (config.@"x11-instance-name") |pn|
+            pn
+        else if (builtin.mode == .Debug)
+            "ghostty-debug"
+        else
+            "ghostty";
+        c.g_set_prgname(prgname);
+        c.gdk_x11_display_set_program_class(display, app_id);
+    }
+
     // This just calls the "activate" signal but its part of the normal
     // startup routine so we just call it:
     // https://gitlab.gnome.org/GNOME/glib/-/blob/bd2ccc2f69ecfd78ca3f34ab59e42e2b462bad65/gio/gapplication.c#L2302
diff --git a/src/apprt/gtk/c.zig b/src/apprt/gtk/c.zig
index 31fc2c1b3..d7e85f376 100644
--- a/src/apprt/gtk/c.zig
+++ b/src/apprt/gtk/c.zig
@@ -1,6 +1,10 @@
 const c = @cImport({
     @cInclude("gtk/gtk.h");
     if (@import("build_options").libadwaita) @cInclude("libadwaita-1/adwaita.h");
+
+    // Add in X11-specific GDK backend which we use for specific things (e.g.
+    // X11 window class).
+    @cInclude("gdk/x11/gdkx.h");
 });
 
 pub usingnamespace c;
diff --git a/src/config/Config.zig b/src/config/Config.zig
index f49d21d82..2b7df501a 100644
--- a/src/config/Config.zig
+++ b/src/config/Config.zig
@@ -366,16 +366,31 @@ fullscreen: bool = false,
 /// set title escape sequences programs (such as Neovim) may send.
 title: ?[:0]const u8 = null,
 
-/// The setting that will change the application class value. This value is
-/// often used with Linux window managers to change behavior (such as
-/// floating vs tiled). If you don't know what this is, don't set it.
+/// The setting that will change the application class value.
+///
+/// This controls the class field of the WM_CLASS X11 property (when running
+/// under X11), and the Wayland application ID (when running under Wayland).
+///
+/// Note that changing this value between invocations will create new, separate
+/// instances, of Ghostty when running with --gtk-single-instance=true. See
+/// that option for more details.
 ///
 /// The class name must follow the GTK requirements defined here:
 /// https://docs.gtk.org/gio/type_func.Application.id_is_valid.html
 ///
+/// The default is "com.mitchellh.ghostty".
+///
 /// This only affects GTK builds.
 class: ?[:0]const u8 = null,
 
+/// This controls the instance name field of the WM_CLASS X11 property when
+/// running under X11. It has no effect otherwise.
+///
+/// The default is "ghostty".
+///
+/// This only affects GTK builds.
+@"x11-instance-name": ?[:0]const u8 = null,
+
 /// The directory to change to after starting the command.
 ///
 /// This setting is secondary to the "window-inherit-working-directory"