diff --git a/Libraries/LibWeb/CMakeLists.txt b/Libraries/LibWeb/CMakeLists.txt
index 77e1622f0eb..9413a99d05c 100644
--- a/Libraries/LibWeb/CMakeLists.txt
+++ b/Libraries/LibWeb/CMakeLists.txt
@@ -170,6 +170,7 @@ set(SOURCES
     CSS/SystemColor.cpp
     CSS/Time.cpp
     CSS/Transformation.cpp
+    CSS/TransitionEvent.cpp
     CSS/VisualViewport.cpp
     Cookie/Cookie.cpp
     Cookie/ParsedCookie.cpp
diff --git a/Libraries/LibWeb/CSS/TransitionEvent.cpp b/Libraries/LibWeb/CSS/TransitionEvent.cpp
new file mode 100644
index 00000000000..6eaaad214a8
--- /dev/null
+++ b/Libraries/LibWeb/CSS/TransitionEvent.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2024, Lucas Chollet <lucas.chollet@serenityos.org>.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "TransitionEvent.h"
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/Bindings/TransitionEventPrototype.h>
+
+namespace Web::CSS {
+
+GC_DEFINE_ALLOCATOR(TransitionEvent);
+
+GC::Ref<TransitionEvent> TransitionEvent::create(JS::Realm& realm, FlyString const& type, TransitionEventInit const& event_init)
+{
+    auto event = realm.create<TransitionEvent>(realm, type, event_init);
+    event->set_is_trusted(true);
+    return event;
+}
+
+GC::Ref<TransitionEvent> TransitionEvent::construct_impl(JS::Realm& realm, FlyString const& type, TransitionEventInit const& event_init)
+{
+    return realm.create<TransitionEvent>(realm, type, event_init);
+}
+
+TransitionEvent::TransitionEvent(JS::Realm& realm, FlyString const& type, TransitionEventInit const& event_init)
+    : DOM::Event(realm, type, event_init)
+    , m_property_name(event_init.property_name)
+    , m_elapsed_time(event_init.elapsed_time)
+    , m_pseudo_element(event_init.pseudo_element)
+{
+}
+
+TransitionEvent::~TransitionEvent() = default;
+
+void TransitionEvent::initialize(JS::Realm& realm)
+{
+    Base::initialize(realm);
+    WEB_SET_PROTOTYPE_FOR_INTERFACE(TransitionEvent);
+}
+
+}
diff --git a/Libraries/LibWeb/CSS/TransitionEvent.h b/Libraries/LibWeb/CSS/TransitionEvent.h
new file mode 100644
index 00000000000..876c71218ad
--- /dev/null
+++ b/Libraries/LibWeb/CSS/TransitionEvent.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2024, Lucas Chollet <lucas.chollet@serenityos.org>.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/DOM/Event.h>
+
+namespace Web::CSS {
+
+struct TransitionEventInit : public DOM::EventInit {
+    String property_name {};
+    double elapsed_time = 0.0;
+    String pseudo_element {};
+};
+
+class TransitionEvent final : public DOM::Event {
+    WEB_PLATFORM_OBJECT(TransitionEvent, DOM::Event);
+    GC_DECLARE_ALLOCATOR(TransitionEvent);
+
+public:
+    [[nodiscard]] static GC::Ref<TransitionEvent> create(JS::Realm&, FlyString const& event_name, TransitionEventInit const& = {});
+    [[nodiscard]] static GC::Ref<TransitionEvent> construct_impl(JS::Realm&, FlyString const& event_name, TransitionEventInit const& = {});
+
+    virtual ~TransitionEvent() override;
+
+    String const& property_name() const { return m_property_name; }
+    double elapsed_time() const { return m_elapsed_time; }
+    String const& pseudo_element() const { return m_pseudo_element; }
+
+private:
+    TransitionEvent(JS::Realm&, FlyString const& event_name, TransitionEventInit const& event_init);
+
+    virtual void initialize(JS::Realm&) override;
+
+    String m_property_name {};
+    double m_elapsed_time {};
+    String m_pseudo_element {};
+};
+}
diff --git a/Libraries/LibWeb/CSS/TransitionEvent.idl b/Libraries/LibWeb/CSS/TransitionEvent.idl
new file mode 100644
index 00000000000..3ead72fccb9
--- /dev/null
+++ b/Libraries/LibWeb/CSS/TransitionEvent.idl
@@ -0,0 +1,16 @@
+#import <DOM/Event.idl>
+
+// https://drafts.csswg.org/css-transitions/#transitionevent
+[Exposed=Window]
+interface TransitionEvent : Event {
+    constructor(CSSOMString type, optional TransitionEventInit transitionEventInitDict = {});
+    readonly attribute CSSOMString propertyName;
+    readonly attribute double elapsedTime;
+    readonly attribute CSSOMString pseudoElement;
+};
+
+dictionary TransitionEventInit : EventInit {
+    CSSOMString propertyName = "";
+    double elapsedTime = 0.0;
+    CSSOMString pseudoElement = "";
+};
diff --git a/Libraries/LibWeb/idl_files.cmake b/Libraries/LibWeb/idl_files.cmake
index 95c1f2ff729..f28e335f6b5 100644
--- a/Libraries/LibWeb/idl_files.cmake
+++ b/Libraries/LibWeb/idl_files.cmake
@@ -46,6 +46,7 @@ libweb_js_bindings(CSS/Screen)
 libweb_js_bindings(CSS/ScreenOrientation)
 libweb_js_bindings(CSS/StyleSheet)
 libweb_js_bindings(CSS/StyleSheetList)
+libweb_js_bindings(CSS/TransitionEvent)
 libweb_js_bindings(CSS/VisualViewport)
 libweb_js_bindings(DOM/AbstractRange)
 libweb_js_bindings(DOM/Attr)
diff --git a/Tests/LibWeb/Text/expected/all-window-properties.txt b/Tests/LibWeb/Text/expected/all-window-properties.txt
index 399e330c996..83c75af1c98 100644
--- a/Tests/LibWeb/Text/expected/all-window-properties.txt
+++ b/Tests/LibWeb/Text/expected/all-window-properties.txt
@@ -381,6 +381,7 @@ ToggleEvent
 TrackEvent
 TransformStream
 TransformStreamDefaultController
+TransitionEvent
 TreeWalker
 TypeError
 UIEvent
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/css-transitions/transitionevent-interface.txt b/Tests/LibWeb/Text/expected/wpt-import/css/css-transitions/transitionevent-interface.txt
new file mode 100644
index 00000000000..c9d096d3812
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/css-transitions/transitionevent-interface.txt
@@ -0,0 +1,46 @@
+Harness status: OK
+
+Found 41 tests
+
+41 Pass
+Pass	the event is an instance of TransitionEvent
+Pass	the event inherts from Event
+Pass	Missing type argument
+Pass	type argument is string
+Pass	type argument is null
+Pass	event type set to undefined
+Pass	propertyName has default value of empty string
+Pass	elapsedTime has default value of 0.0
+Pass	propertyName is readonly
+Pass	elapsedTime is readonly
+Pass	animationEventInit argument is null
+Pass	animationEventInit argument is undefined
+Pass	animationEventInit argument is empty dictionary
+Pass	TransitionEvent.pseudoElement initialized from the dictionary
+Pass	propertyName set to 'sample'
+Pass	propertyName set to undefined
+Pass	propertyName set to null
+Pass	propertyName set to false
+Pass	propertyName set to true
+Pass	propertyName set to a number
+Pass	propertyName set to []
+Pass	propertyName set to [1, 2, 3]
+Pass	propertyName set to an object
+Pass	propertyName set to an object with a valueOf function
+Pass	elapsedTime set to 0.5
+Pass	elapsedTime set to -0.5
+Pass	elapsedTime set to undefined
+Pass	elapsedTime set to null
+Pass	elapsedTime set to false
+Pass	elapsedTime set to true
+Pass	elapsedTime set to ''
+Pass	elapsedTime set to []
+Pass	elapsedTime set to [0.5]
+Pass	elapsedTime set to an object with a valueOf function
+Pass	elapsedTime cannot be set to NaN
+Pass	elapsedTime cannot be set to Infinity
+Pass	elapsedTime cannot be set to -Infinity
+Pass	elapsedTime cannot be set to 'sample'
+Pass	elapsedTime cannot be set to [0.5, 1.0]
+Pass	elapsedTime cannot be set to an object
+Pass	TransitionEventInit properties set value
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/css-transitions/transitionevent-interface.html b/Tests/LibWeb/Text/input/wpt-import/css/css-transitions/transitionevent-interface.html
new file mode 100644
index 00000000000..b72e21d50a8
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/css-transitions/transitionevent-interface.html
@@ -0,0 +1,229 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Transitions Test: TransitionEvent interface</title>
+<link rel="help" href="https://drafts.csswg.org/css-transitions-1/#interface-transitionevent">
+
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<script src="transitionevent-interface.js"></script>
+
+<script>
+test(function() {
+  var event = new TransitionEvent("");
+  assert_true(event instanceof window.TransitionEvent);
+}, "the event is an instance of TransitionEvent");
+
+test(function() {
+  var event = new TransitionEvent("");
+  assert_true(event instanceof window.Event);
+}, "the event inherts from Event");
+
+test(function() {
+  assert_throws_js(TypeError, function() {
+    new TransitionEvent();
+  }, 'First argument is required, so was expecting a TypeError.');
+}, 'Missing type argument');
+
+test(function() {
+  var event = new TransitionEvent("test");
+  assert_equals(event.type, "test");
+}, "type argument is string");
+
+test(function() {
+  var event = new TransitionEvent(null);
+  assert_equals(event.type, "null");
+}, "type argument is null");
+
+test(function() {
+  var event = new TransitionEvent(undefined);
+  assert_equals(event.type, "undefined");
+}, "event type set to undefined");
+
+test(function() {
+  var event = new TransitionEvent("test");
+  assert_equals(event.propertyName, "");
+}, "propertyName has default value of empty string");
+
+test(function() {
+  var event = new TransitionEvent("test");
+  assert_equals(event.elapsedTime, 0.0);
+}, "elapsedTime has default value of 0.0");
+
+test(function() {
+  var event = new TransitionEvent("test");
+  assert_readonly(event, "propertyName", "readonly attribute value");
+}, "propertyName is readonly");
+
+test(function() {
+  var event = new TransitionEvent("test");
+  assert_readonly(event, "elapsedTime", "readonly attribute value");
+}, "elapsedTime is readonly");
+
+test(function() {
+  var event = new TransitionEvent("test", null);
+  assert_equals(event.propertyName, "");
+  assert_equals(event.elapsedTime, 0.0);
+}, "animationEventInit argument is null");
+
+test(function() {
+  var event = new TransitionEvent("test", undefined);
+  assert_equals(event.propertyName, "");
+  assert_equals(event.elapsedTime, 0.0);
+}, "animationEventInit argument is undefined");
+
+test(function() {
+  var event = new TransitionEvent("test", {});
+  assert_equals(event.propertyName, "");
+  assert_equals(event.elapsedTime, 0.0);
+}, "animationEventInit argument is empty dictionary");
+
+test(function() {
+  var event = new TransitionEvent("test", {pseudoElement: "::testPseudo"});
+  assert_equals(event.pseudoElement, "::testPseudo");
+}, "TransitionEvent.pseudoElement initialized from the dictionary");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: "sample"});
+  assert_equals(event.propertyName, "sample");
+}, "propertyName set to 'sample'");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: undefined});
+  assert_equals(event.propertyName, "");
+}, "propertyName set to undefined");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: null});
+  assert_equals(event.propertyName, "null");
+}, "propertyName set to null");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: false});
+  assert_equals(event.propertyName, "false");
+}, "propertyName set to false");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: true});
+  assert_equals(event.propertyName, "true");
+}, "propertyName set to true");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: 0.5});
+  assert_equals(event.propertyName, "0.5");
+}, "propertyName set to a number");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: []});
+  assert_equals(event.propertyName, "");
+}, "propertyName set to []");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: [1, 2, 3]});
+  assert_equals(event.propertyName, "1,2,3");
+}, "propertyName set to [1, 2, 3]");
+
+test(function() {
+  var event = new TransitionEvent("test", {propertyName: {sample: 0.5}});
+  assert_equals(event.propertyName, "[object Object]");
+}, "propertyName set to an object");
+
+test(function() {
+  var event = new TransitionEvent("test",
+      {propertyName: {valueOf: function () { return 'sample'; }}});
+  assert_equals(event.propertyName, "[object Object]");
+}, "propertyName set to an object with a valueOf function");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: 0.5});
+  assert_equals(event.elapsedTime, 0.5);
+}, "elapsedTime set to 0.5");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: -0.5});
+  assert_equals(event.elapsedTime, -0.5);
+}, "elapsedTime set to -0.5");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: undefined});
+  assert_equals(event.elapsedTime, 0);
+}, "elapsedTime set to undefined");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: null});
+  assert_equals(event.elapsedTime, 0);
+}, "elapsedTime set to null");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: false});
+  assert_equals(event.elapsedTime, 0);
+}, "elapsedTime set to false");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: true});
+  assert_equals(event.elapsedTime, 1);
+}, "elapsedTime set to true");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: ""});
+  assert_equals(event.elapsedTime, 0);
+}, "elapsedTime set to ''");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: []});
+  assert_equals(event.elapsedTime, 0);
+}, "elapsedTime set to []");
+
+test(function() {
+  var event = new TransitionEvent("test", {elapsedTime: [0.5]});
+  assert_equals(event.elapsedTime, 0.5);
+}, "elapsedTime set to [0.5]");
+
+test(function() {
+  var event = new TransitionEvent(
+      "test", {elapsedTime: { valueOf: function() { return 0.5; }}});
+  assert_equals(event.elapsedTime, 0.5);
+}, "elapsedTime set to an object with a valueOf function");
+
+test(function() {
+  assert_throws_js(TypeError, function() {
+    new TransitionEvent("test", {elapsedTime: NaN});
+  }, 'elapsedTime cannot be NaN so was expecting a TypeError');
+}, "elapsedTime cannot be set to NaN");
+
+test(function() {
+  assert_throws_js(TypeError, function() {
+    new TransitionEvent("test", {elapsedTime: Infinity});
+  }, 'elapsedTime cannot be Infinity so was expecting a TypeError');
+}, "elapsedTime cannot be set to Infinity");
+
+test(function() {
+  assert_throws_js(TypeError, function() {
+    new TransitionEvent("test", {elapsedTime: -Infinity});
+  }, 'elapsedTime cannot be -Infinity so was expecting a TypeError');
+}, "elapsedTime cannot be set to -Infinity");
+
+test(function() {
+  assert_throws_js(TypeError, function() {
+    new TransitionEvent("test", {elapsedTime: "sample"});
+  }, 'elapsedTime cannot be a string so was expecting a TypeError');
+}, "elapsedTime cannot be set to 'sample'");
+
+test(function() {
+  assert_throws_js(TypeError, function() {
+    new TransitionEvent("test", {elapsedTime: [0.5, 1.0]});
+  }, 'elapsedTime cannot be a multi-element array so was expecting a TypeError');
+}, "elapsedTime cannot be set to [0.5, 1.0]");
+
+test(function() {
+  assert_throws_js(TypeError, function() {
+    new TransitionEvent("test", {elapsedTime: { sample: 0.5}});
+  }, 'elapsedTime cannot be an object so was expecting a TypeError');
+}, "elapsedTime cannot be set to an object");
+
+test(function() {
+  var eventInit = {propertyName: "sample", elapsedTime: 0.5};
+  var event = new TransitionEvent("test", eventInit);
+  assert_equals(event.propertyName, "sample");
+  assert_equals(event.elapsedTime, 0.5);
+}, "TransitionEventInit properties set value");
+</script>