diff --git a/CMakeLists.txt b/CMakeLists.txt
index da9f07e..b61d0d9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -26,6 +26,6 @@ set (CMAKE_CXX_STANDARD 17)
 add_subdirectory(src)
 
 option(NFD_BUILD_TESTS "Build tests for nfd" OFF)
-if(${NFD_BUILD_TESTS})
+if(NFD_BUILD_TESTS)
     add_subdirectory(test)
 endif()
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ac776e9..e67647d 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -12,8 +12,27 @@ endif()
 
 if(nfd_PLATFORM STREQUAL PLATFORM_LINUX)
   find_package(PkgConfig REQUIRED)
-  pkg_check_modules(GTK3 REQUIRED gtk+-3.0)
-  message("Using GTK version: ${GTK3_VERSION}")
+  set(NFD_GTK_VERSION "" CACHE STRING "GTK version for Linux builds ('3' or '4')")
+  set_property(CACHE NFD_GTK_VERSION PROPERTY STRINGS "" 3 4)
+  # For Linux, we support both GTK3 and GTK4.
+  # If NFD_GTK_VERSION is not explicitly set, then we take one that is available.
+  # Otherwise, we find the version that the user wants.
+  if(NFD_GTK_VERSION STREQUAL "")
+    pkg_search_module(GTK REQUIRED gtk+-3.0 gtk4)
+    if(DEFINED GTK_gtk+-3.0_VERSION)
+      set(GTK_VERSION ${GTK_gtk+-3.0_VERSION})
+    elseif(DEFINED GTK_gtk4_VERSION)
+      set(GTK_VERSION ${GTK_gtk4_VERSION})
+    endif()
+  elseif(NFD_GTK_VERSION STREQUAL 3)
+    pkg_check_modules(GTK REQUIRED gtk+-3.0)
+  elseif(NFD_GTK_VERSION STREQUAL 4)
+    pkg_check_modules(GTK REQUIRED gtk4)
+  else()
+    message(FATAL_ERROR "Unsupported GTK version: ${NFD_GTK_VERSION}")
+  endif()
+
+  message("Using GTK version: ${GTK_VERSION}")
   list(APPEND SOURCE_FILES nfd_gtk.cpp)
 endif()
 
@@ -32,9 +51,9 @@ target_include_directories(${TARGET_NAME}
 
 if(nfd_PLATFORM STREQUAL PLATFORM_LINUX)
   target_include_directories(${TARGET_NAME}
-    PRIVATE ${GTK3_INCLUDE_DIRS})
+    PRIVATE ${GTK_INCLUDE_DIRS})
   target_link_libraries(${TARGET_NAME}
-    PRIVATE ${GTK3_LIBRARIES})
+    PRIVATE ${GTK_LIBRARIES})
 endif()
 
 if(nfd_PLATFORM STREQUAL PLATFORM_MACOS)
diff --git a/src/nfd_gtk.cpp b/src/nfd_gtk.cpp
index 29d7dc0..d4a37a7 100644
--- a/src/nfd_gtk.cpp
+++ b/src/nfd_gtk.cpp
@@ -5,12 +5,18 @@
   Authors: Bernard Teo, Michael Labbe
 
   Note: We do not check for malloc failure on Linux - Linux overcommits memory!
+  Note: The GTK4 implementation does not distinguish between local and network files,
+  so it is possible for the file picker to return a network URI instead of a local filename.
 */
 
 #include <assert.h>
 #include <gtk/gtk.h>
 #if defined(GDK_WINDOWING_X11)
+#if GTK_MAJOR_VERSION == 3
 #include <gdk/gdkx.h>
+#elif GTK_MAJOR_VERSION == 4
+#include <gdk/x11/gdkx.h>
+#endif
 #endif
 #include <stddef.h>
 #include <stdio.h>
@@ -19,6 +25,8 @@
 
 #include "nfd.h"
 
+#define UNSUPPORTED_ERROR() static_assert(false, "Unsupported GTK version, this is an NFD bug.")
+
 namespace {
 
 template <typename T>
@@ -37,6 +45,14 @@ struct FreeCheck_Guard {
     }
 };
 
+template <typename T>
+struct GUnref_Guard {
+    T* data;
+    GUnref_Guard(T* object) noexcept : data(object) {}
+    ~GUnref_Guard() { g_object_unref(data); }
+    T* get() const noexcept { return data; }
+};
+
 /* current error */
 const char* g_errorstr = nullptr;
 
@@ -278,16 +294,33 @@ Pair_GtkFileFilter_FileExtension* AddFiltersToDialogWithMap(GtkFileChooser* choo
     return map;
 }
 
-void SetDefaultPath(GtkFileChooser* chooser, const char* defaultPath) {
-    if (!defaultPath || !*defaultPath) return;
+/*
+Note: GTK+ manual recommends not specifically setting the default path.
+We do it anyway in order to be consistent across platforms.
 
-    /* GTK+ manual recommends not specifically setting the default path.
-    We do it anyway in order to be consistent across platforms.
+If consistency with the native OS is preferred,
+then this function should be made a no-op.
+*/
+#if GTK_MAJOR_VERSION == 3
+nfdresult_t SetDefaultPath(GtkFileChooser* chooser, const char* defaultPath) {
+    if (!defaultPath || !*defaultPath) return NFD_OKAY;
 
-    If consistency with the native OS is preferred, this is the line
-    to comment out. -ml */
     gtk_file_chooser_set_current_folder(chooser, defaultPath);
+    return NFD_OKAY;
+}
+#elif GTK_MAJOR_VERSION == 4
+nfdresult_t SetDefaultPath(GtkFileChooser* chooser, const char* defaultPath) {
+    if (!defaultPath || !*defaultPath) return NFD_OKAY;
+
+    GUnref_Guard<GFile> file(g_file_new_for_path(defaultPath));
+
+    if (!gtk_file_chooser_set_current_folder(chooser, file.get(), nullptr)) {
+        NFDi_SetError("Failed to set default path.");
+        return NFD_ERROR;
+    }
+    return NFD_OKAY;
 }
+#endif
 
 void SetDefaultName(GtkFileChooser* chooser, const char* defaultName) {
     if (!defaultName || !*defaultName) return;
@@ -295,8 +328,26 @@ void SetDefaultName(GtkFileChooser* chooser, const char* defaultName) {
     gtk_file_chooser_set_current_name(chooser, defaultName);
 }
 
+char* GetSingleFileName(GtkFileChooser* chooser) {
+#if GTK_MAJOR_VERSION == 3
+    return gtk_file_chooser_get_filename(chooser);
+#elif GTK_MAJOR_VERSION == 4
+    GUnref_Guard<GFile> file(gtk_file_chooser_get_file(chooser));
+    return g_file_get_path(file.get());
+#else
+    UNSUPPORTED_ERROR();
+#endif
+}
+
 void WaitForCleanup() {
+#if GTK_MAJOR_VERSION == 3
     while (gtk_events_pending()) gtk_main_iteration();
+#elif GTK_MAJOR_VERSION == 4
+    while (g_main_context_iteration(NULL, FALSE))
+        ;
+#else
+    UNSUPPORTED_ERROR();
+#endif
 }
 
 struct Widget_Guard {
@@ -304,7 +355,13 @@ struct Widget_Guard {
     Widget_Guard(GtkWidget* widget) : data(widget) {}
     ~Widget_Guard() {
         WaitForCleanup();
+#if GTK_MAJOR_VERSION == 3
         gtk_widget_destroy(data);
+#elif GTK_MAJOR_VERSION == 4
+        gtk_window_destroy(GTK_WINDOW(data));
+#else
+        UNSUPPORTED_ERROR();
+#endif
         WaitForCleanup();
     }
 };
@@ -362,12 +419,20 @@ void FileActivatedSignalHandler(GtkButton* saveButton, void* userdata) {
     g_free(currentFileName);
 }
 
+#if GTK_MAJOR_VERSION == 4
+void DialogResponseHandler(GtkDialog*, gint resp, gpointer out_resp_gp) {
+    gint* out_resp = static_cast<gint*>(out_resp_gp);
+    *out_resp = resp;
+}
+#endif
+
 // wrapper for gtk_dialog_run() that brings the dialog to the front
 // see issues at:
 // https://github.com/btzy/nativefiledialog-extended/issues/31
 // https://github.com/mlabbe/nativefiledialog/pull/92
 // https://github.com/guillaumechereau/noc/pull/11
 gint RunDialogWithFocus(GtkDialog* dialog) {
+#if GTK_MAJOR_VERSION == 3
 #if defined(GDK_WINDOWING_X11)
     gtk_widget_show_all(GTK_WIDGET(dialog));  // show the dialog so that it gets a display
     if (GDK_IS_X11_DISPLAY(gtk_widget_get_display(GTK_WIDGET(dialog)))) {
@@ -379,6 +444,20 @@ gint RunDialogWithFocus(GtkDialog* dialog) {
     }
 #endif
     return gtk_dialog_run(dialog);
+#elif GTK_MAJOR_VERSION == 4
+    // TODO: the X11 popup issues
+    gtk_window_set_modal(GTK_WINDOW(dialog), TRUE);
+    gtk_widget_show(GTK_WIDGET(dialog));
+    gint resp = 0;
+    g_signal_connect(G_OBJECT(dialog),
+                     "response",
+                     G_CALLBACK(DialogResponseHandler),
+                     static_cast<gpointer>(&resp));
+    while (resp == 0) g_main_context_iteration(NULL, TRUE);
+    return resp;
+#else
+    UNSUPPORTED_ERROR();
+#endif
 }
 
 }  // namespace
@@ -395,7 +474,14 @@ void NFD_ClearError(void) {
 
 nfdresult_t NFD_Init(void) {
     // Init GTK
-    if (!gtk_init_check(NULL, NULL)) {
+#if GTK_MAJOR_VERSION == 3
+    if (!gtk_init_check(NULL, NULL))
+#elif GTK_MAJOR_VERSION == 4
+    if (!gtk_init_check())
+#else
+    UNSUPPORTED_ERROR();
+#endif
+    {
         NFDi_SetError("gtk_init_check failed to initilaize GTK+");
         return NFD_ERROR;
     }
@@ -430,13 +516,14 @@ nfdresult_t NFD_OpenDialogN(nfdnchar_t** outPath,
     AddFiltersToDialog(GTK_FILE_CHOOSER(widget), filterList, filterCount);
 
     /* Set the default path */
-    SetDefaultPath(GTK_FILE_CHOOSER(widget), defaultPath);
+    nfdresult_t res = SetDefaultPath(GTK_FILE_CHOOSER(widget), defaultPath);
+    if (res != NFD_OKAY) return res;
 
     if (RunDialogWithFocus(GTK_DIALOG(widget)) == GTK_RESPONSE_ACCEPT) {
         // write out the file name
-        *outPath = gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(widget));
+        *outPath = GetSingleFileName(GTK_FILE_CHOOSER(widget));
 
-        return NFD_OKAY;
+        return *outPath ? NFD_OKAY : NFD_CANCEL;
     } else {
         return NFD_CANCEL;
     }
@@ -465,7 +552,8 @@ nfdresult_t NFD_OpenDialogMultipleN(const nfdpathset_t** outPaths,
     AddFiltersToDialog(GTK_FILE_CHOOSER(widget), filterList, filterCount);
 
     /* Set the default path */
-    SetDefaultPath(GTK_FILE_CHOOSER(widget), defaultPath);
+    nfdresult_t res = SetDefaultPath(GTK_FILE_CHOOSER(widget), defaultPath);
+    if (res != NFD_OKAY) return res;
 
     if (RunDialogWithFocus(GTK_DIALOG(widget)) == GTK_RESPONSE_ACCEPT) {
         // write out the file name
@@ -495,8 +583,10 @@ nfdresult_t NFD_SaveDialogN(nfdnchar_t** outPath,
 
     GtkWidget* saveButton = gtk_dialog_add_button(GTK_DIALOG(widget), "_Save", GTK_RESPONSE_ACCEPT);
 
-    // Prompt on overwrite
+    // Prompt on overwrite (GTK3 only, because GTK4 automatically prompts)
+#if GTK_MAJOR_VERSION == 3
     gtk_file_chooser_set_do_overwrite_confirmation(GTK_FILE_CHOOSER(widget), TRUE);
+#endif
 
     /* Build the filter list */
     ButtonClickedArgs buttonClickedArgs;
@@ -505,7 +595,8 @@ nfdresult_t NFD_SaveDialogN(nfdnchar_t** outPath,
         AddFiltersToDialogWithMap(GTK_FILE_CHOOSER(widget), filterList, filterCount);
 
     /* Set the default path */
-    SetDefaultPath(GTK_FILE_CHOOSER(widget), defaultPath);
+    nfdresult_t res = SetDefaultPath(GTK_FILE_CHOOSER(widget), defaultPath);
+    if (res != NFD_OKAY) return res;
 
     /* Set the default file name */
     SetDefaultName(GTK_FILE_CHOOSER(widget), defaultName);
@@ -526,9 +617,9 @@ nfdresult_t NFD_SaveDialogN(nfdnchar_t** outPath,
 
     if (result == GTK_RESPONSE_ACCEPT) {
         // write out the file name
-        *outPath = gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(widget));
+        *outPath = GetSingleFileName(GTK_FILE_CHOOSER(widget));
 
-        return NFD_OKAY;
+        return *outPath ? NFD_OKAY : NFD_CANCEL;
     } else {
         return NFD_CANCEL;
     }
@@ -548,13 +639,14 @@ nfdresult_t NFD_PickFolderN(nfdnchar_t** outPath, const nfdnchar_t* defaultPath)
     Widget_Guard widgetGuard(widget);
 
     /* Set the default path */
-    SetDefaultPath(GTK_FILE_CHOOSER(widget), defaultPath);
+    nfdresult_t res = SetDefaultPath(GTK_FILE_CHOOSER(widget), defaultPath);
+    if (res != NFD_OKAY) return res;
 
     if (RunDialogWithFocus(GTK_DIALOG(widget)) == GTK_RESPONSE_ACCEPT) {
         // write out the file name
-        *outPath = gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(widget));
+        *outPath = GetSingleFileName(GTK_FILE_CHOOSER(widget));
 
-        return NFD_OKAY;
+        return *outPath ? NFD_OKAY : NFD_CANCEL;
     } else {
         return NFD_CANCEL;
     }