diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index 6362a06d5fd4da6..38fb7e99b8b4d43 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -499,6 +499,17 @@ WebIDL::ExceptionOr<Document*> Document::open(String const&, String const&)
     return this;
 }
 
+// https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#dom-document-open-window
+WebIDL::ExceptionOr<JS::GCPtr<HTML::WindowProxy>> Document::open(String const& url, String const& name, String const& features)
+{
+    // 1. If this is not fully active, then throw an "InvalidAccessError" DOMException exception.
+    if (!is_fully_active())
+        return WebIDL::InvalidAccessError::create(realm(), "Cannot perform open on a document that isn't fully active."sv);
+
+    // 2. Return the result of running the window open steps with url, name, and features.
+    return window().open_impl(url, name, features);
+}
+
 // https://html.spec.whatwg.org/multipage/dynamic-markup-insertion.html#closing-the-input-stream
 WebIDL::ExceptionOr<void> Document::close()
 {
diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index 3cf09999a2fc8a1..b55e7284f6fa242 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -33,6 +33,7 @@
 #include <LibWeb/HTML/Scripting/Environments.h>
 #include <LibWeb/HTML/VisibilityState.h>
 #include <LibWeb/HTML/Window.h>
+#include <LibWeb/HTML/WindowProxy.h>
 #include <LibWeb/WebIDL/ExceptionOr.h>
 
 namespace Web::DOM {
@@ -295,6 +296,7 @@ class Document
     WebIDL::ExceptionOr<void> writeln(Vector<String> const& strings);
 
     WebIDL::ExceptionOr<Document*> open(String const& = "", String const& = "");
+    WebIDL::ExceptionOr<JS::GCPtr<HTML::WindowProxy>> open(String const& url, String const& name, String const& features);
     WebIDL::ExceptionOr<void> close();
 
     HTML::Window* default_view() { return m_window.ptr(); }
diff --git a/Userland/Libraries/LibWeb/DOM/Document.idl b/Userland/Libraries/LibWeb/DOM/Document.idl
index 1c667c7e84f42a8..473d59254b9842b 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.idl
+++ b/Userland/Libraries/LibWeb/DOM/Document.idl
@@ -43,8 +43,7 @@ interface Document : Node {
     readonly attribute Window? defaultView;
 
     [CEReactions] Document open(optional DOMString unused1, optional DOMString unused2);
-    // FIXME: implement ExceptionOr<HTML::Window> Document::open(...)
-    // WindowProxy? open(USVString url, DOMString name, DOMString features);
+    WindowProxy? open(USVString url, DOMString name, DOMString features);
     [CEReactions] undefined close();
     [CEReactions] undefined write(DOMString... text);
     [CEReactions] undefined writeln(DOMString... text);