diff --git a/Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp b/Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp
index 71176cf4f60..ccdb1204f3b 100644
--- a/Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp
+++ b/Userland/Libraries/LibWeb/Bindings/EventWrapperFactory.cpp
@@ -1,10 +1,12 @@
 /*
  * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #include <LibWeb/Bindings/CloseEventWrapper.h>
+#include <LibWeb/Bindings/CustomEventWrapper.h>
 #include <LibWeb/Bindings/EventWrapper.h>
 #include <LibWeb/Bindings/EventWrapperFactory.h>
 #include <LibWeb/Bindings/MessageEventWrapper.h>
@@ -17,6 +19,8 @@ namespace Web::Bindings {
 
 EventWrapper* wrap(JS::GlobalObject& global_object, DOM::Event& event)
 {
+    if (is<DOM::CustomEvent>(event))
+        return static_cast<CustomEventWrapper*>(wrap_impl(global_object, static_cast<DOM::CustomEvent&>(event)));
     if (is<HTML::CloseEvent>(event))
         return static_cast<CloseEventWrapper*>(wrap_impl(global_object, static_cast<HTML::CloseEvent&>(event)));
     if (is<HTML::MessageEvent>(event))
diff --git a/Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h b/Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h
index 303ebb0f92a..fd79b55a683 100644
--- a/Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h
+++ b/Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h
@@ -22,6 +22,8 @@
 #include <LibWeb/Bindings/CloseEventPrototype.h>
 #include <LibWeb/Bindings/CommentConstructor.h>
 #include <LibWeb/Bindings/CommentPrototype.h>
+#include <LibWeb/Bindings/CustomEventConstructor.h>
+#include <LibWeb/Bindings/CustomEventPrototype.h>
 #include <LibWeb/Bindings/DOMExceptionConstructor.h>
 #include <LibWeb/Bindings/DOMExceptionPrototype.h>
 #include <LibWeb/Bindings/DOMImplementationConstructor.h>
@@ -265,6 +267,7 @@
     ADD_WINDOW_OBJECT_INTERFACE(CharacterData)             \
     ADD_WINDOW_OBJECT_INTERFACE(CloseEvent)                \
     ADD_WINDOW_OBJECT_INTERFACE(Comment)                   \
+    ADD_WINDOW_OBJECT_INTERFACE(CustomEvent)               \
     ADD_WINDOW_OBJECT_INTERFACE(CSSStyleSheet)             \
     ADD_WINDOW_OBJECT_INTERFACE(DocumentFragment)          \
     ADD_WINDOW_OBJECT_INTERFACE(Document)                  \
diff --git a/Userland/Libraries/LibWeb/CMakeLists.txt b/Userland/Libraries/LibWeb/CMakeLists.txt
index 7df24978b99..e7c89a9f2e9 100644
--- a/Userland/Libraries/LibWeb/CMakeLists.txt
+++ b/Userland/Libraries/LibWeb/CMakeLists.txt
@@ -45,6 +45,7 @@ set(SOURCES
     DOM/CharacterData.cpp
     DOM/CharacterData.idl
     DOM/Comment.cpp
+    DOM/CustomEvent.cpp
     DOM/DOMImplementation.cpp
     DOM/Document.cpp
     DOM/DocumentFragment.cpp
@@ -328,6 +329,7 @@ libweb_js_wrapper(DOM/AbortController)
 libweb_js_wrapper(DOM/AbortSignal)
 libweb_js_wrapper(DOM/CharacterData)
 libweb_js_wrapper(DOM/Comment)
+libweb_js_wrapper(DOM/CustomEvent)
 libweb_js_wrapper(DOM/Document)
 libweb_js_wrapper(DOM/DocumentFragment)
 libweb_js_wrapper(DOM/DocumentType)
diff --git a/Userland/Libraries/LibWeb/DOM/CustomEvent.cpp b/Userland/Libraries/LibWeb/DOM/CustomEvent.cpp
new file mode 100644
index 00000000000..17c414f910b
--- /dev/null
+++ b/Userland/Libraries/LibWeb/DOM/CustomEvent.cpp
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/DOM/CustomEvent.h>
+
+namespace Web::DOM {
+
+CustomEvent::CustomEvent(FlyString const& event_name)
+    : Event(event_name)
+{
+}
+
+CustomEvent::~CustomEvent()
+{
+}
+
+void CustomEvent::visit_edges(JS::Cell::Visitor& visitor)
+{
+    visitor.visit(m_detail);
+}
+
+// https://dom.spec.whatwg.org/#dom-customevent-initcustomevent
+void CustomEvent::init_custom_event(String const& type, bool bubbles, bool cancelable, JS::Value detail)
+{
+    // 1. If this’s dispatch flag is set, then return.
+    if (dispatched())
+        return;
+
+    // 2. Initialize this with type, bubbles, and cancelable.
+    initialize(type, bubbles, cancelable);
+
+    // 3. Set this’s detail attribute to detail.
+    m_detail = detail;
+}
+
+}
diff --git a/Userland/Libraries/LibWeb/DOM/CustomEvent.h b/Userland/Libraries/LibWeb/DOM/CustomEvent.h
new file mode 100644
index 00000000000..ad4efe04993
--- /dev/null
+++ b/Userland/Libraries/LibWeb/DOM/CustomEvent.h
@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/DOM/Event.h>
+
+namespace Web::DOM {
+
+// https://dom.spec.whatwg.org/#customevent
+class CustomEvent : public Event {
+public:
+    using WrapperType = Bindings::CustomEventWrapper;
+
+    static NonnullRefPtr<CustomEvent> create(FlyString const& event_name)
+    {
+        return adopt_ref(*new CustomEvent(event_name));
+    }
+
+    virtual ~CustomEvent() override;
+
+    // https://dom.spec.whatwg.org/#dom-customevent-detail
+    JS::Value detail() const { return m_detail; }
+
+    void visit_edges(JS::Cell::Visitor&);
+
+    void init_custom_event(String const& type, bool bubbles, bool cancelable, JS::Value detail);
+
+private:
+    CustomEvent(FlyString const&);
+
+    // https://dom.spec.whatwg.org/#dom-customevent-initcustomevent-type-bubbles-cancelable-detail-detail
+    JS::Value m_detail { JS::js_null() };
+};
+
+}
diff --git a/Userland/Libraries/LibWeb/DOM/CustomEvent.idl b/Userland/Libraries/LibWeb/DOM/CustomEvent.idl
new file mode 100644
index 00000000000..53abba31ac1
--- /dev/null
+++ b/Userland/Libraries/LibWeb/DOM/CustomEvent.idl
@@ -0,0 +1,8 @@
+[Exposed=(Window,Worker), CustomVisit]
+interface CustomEvent : Event {
+    // FIXME: constructor(DOMString type, optional CustomEventInit eventInitDict = {});
+
+    readonly attribute any detail;
+
+    undefined initCustomEvent(DOMString type, optional boolean bubbles = false, optional boolean cancelable = false, optional any detail = null);
+};
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index 875a36e0a4b..f16a5bd203f 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -18,6 +18,7 @@
 #include <LibWeb/CSS/StyleComputer.h>
 #include <LibWeb/Cookie/ParsedCookie.h>
 #include <LibWeb/DOM/Comment.h>
+#include <LibWeb/DOM/CustomEvent.h>
 #include <LibWeb/DOM/DOMException.h>
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/DocumentFragment.h>
@@ -739,7 +740,7 @@ NonnullRefPtr<Event> Document::create_event(const String& interface)
     } else if (interface_lowercase == "compositionevent") {
         event = Event::create(""); // FIXME: Create CompositionEvent
     } else if (interface_lowercase == "customevent") {
-        event = Event::create(""); // FIXME: Create CustomEvent
+        event = CustomEvent::create("");
     } else if (interface_lowercase == "devicemotionevent") {
         event = Event::create(""); // FIXME: Create DeviceMotionEvent
     } else if (interface_lowercase == "deviceorientationevent") {
diff --git a/Userland/Libraries/LibWeb/Forward.h b/Userland/Libraries/LibWeb/Forward.h
index 241a09e83dc..70d9eb29fcc 100644
--- a/Userland/Libraries/LibWeb/Forward.h
+++ b/Userland/Libraries/LibWeb/Forward.h
@@ -62,6 +62,7 @@ class AbortController;
 class AbortSignal;
 class CharacterData;
 class Comment;
+class CustomEvent;
 class Document;
 class DocumentFragment;
 class DocumentLoadEventDelayer;
@@ -261,6 +262,7 @@ class CanvasRenderingContext2DWrapper;
 class CharacterDataWrapper;
 class CloseEventWrapper;
 class CommentWrapper;
+class CustomEventWrapper;
 class DocumentFragmentWrapper;
 class DocumentTypeWrapper;
 class DocumentWrapper;