diff --git a/Userland/CMakeLists.txt b/Userland/CMakeLists.txt
index 537180a29cf..8bc84894ac6 100644
--- a/Userland/CMakeLists.txt
+++ b/Userland/CMakeLists.txt
@@ -22,6 +22,7 @@ target_link_libraries(copy LibGUI)
 target_link_libraries(disasm LibX86)
 target_link_libraries(expr LibRegex)
 target_link_libraries(functrace LibDebug LibX86)
+target_link_libraries(gml-format LibGUI)
 target_link_libraries(html LibWeb)
 target_link_libraries(js LibJS LibLine)
 target_link_libraries(keymap LibKeyboard)
diff --git a/Userland/gml-format.cpp b/Userland/gml-format.cpp
new file mode 100644
index 00000000000..79ce530a327
--- /dev/null
+++ b/Userland/gml-format.cpp
@@ -0,0 +1,105 @@
+/*
+ * Copyright (c) 2021, Linus Groh <mail@linusgroh.de>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <LibCore/ArgsParser.h>
+#include <LibCore/File.h>
+#include <LibGUI/GMLFormatter.h>
+
+bool format_file(const StringView&, bool);
+
+bool format_file(const StringView& path, bool inplace)
+{
+    auto read_from_stdin = path == "-";
+    RefPtr<Core::File> file;
+    if (read_from_stdin) {
+        file = Core::File::standard_input();
+    } else {
+        auto open_mode = inplace ? Core::File::ReadWrite : Core::File::ReadOnly;
+        auto file_or_error = Core::File::open(path, open_mode);
+        if (file_or_error.is_error()) {
+            warnln("Could not open {}: {}", path, file_or_error.error());
+            return false;
+        }
+        file = file_or_error.value();
+    }
+    auto formatted_gml = GUI::format_gml(file->read_all());
+    if (formatted_gml.is_null()) {
+        warnln("Failed to parse GML!");
+        return false;
+    }
+    if (inplace && !read_from_stdin) {
+        if (!file->seek(0) || !file->truncate(0)) {
+            warnln("Could not truncate {}: {}", path, file->error_string());
+            return false;
+        }
+        if (!file->write(formatted_gml)) {
+            warnln("Could not write to {}: {}", path, file->error_string());
+            return false;
+        }
+    } else {
+        out("{}", formatted_gml);
+    }
+    return true;
+}
+
+int main(int argc, char** argv)
+{
+#ifdef __serenity__
+    if (pledge("stdio rpath wpath cpath", nullptr) < 0) {
+        perror("pledge");
+        return 1;
+    }
+#endif
+
+    bool inplace = false;
+    Vector<const char*> files;
+
+    Core::ArgsParser args_parser;
+    args_parser.set_general_help("Format GML files.");
+    args_parser.add_option(inplace, "Write formatted contents back to file rather than standard output", "inplace", 'i');
+    args_parser.add_positional_argument(files, "File(s) to process", "path", Core::ArgsParser::Required::No);
+    args_parser.parse(argc, argv);
+
+#ifdef __serenity__
+    if (!inplace) {
+        if (pledge("stdio rpath", nullptr) < 0) {
+            perror("pledge");
+            return 1;
+        }
+    }
+#endif
+
+    unsigned exit_code = 0;
+
+    if (files.is_empty())
+        files.append("-");
+    for (auto& file : files) {
+        if (!format_file(file, inplace))
+            exit_code = 1;
+    }
+
+    return exit_code;
+}