diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
index fc25620a35a..b4fc0d0c780 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.cpp
@@ -223,6 +223,16 @@ Value calendar_day_of_year(GlobalObject& global_object, Object& calendar, Object
     return calendar.invoke(vm.names.dayOfYear, &date_like);
 }
 
+// 12.1.15 CalendarWeekOfYear ( calendar, dateLike ), https://tc39.es/proposal-temporal/#sec-temporal-calendarweekofyear
+Value calendar_week_of_year(GlobalObject& global_object, Object& calendar, Object& date_like)
+{
+    auto& vm = global_object.vm();
+    // 1. Assert: Type(calendar) is Object.
+
+    // 2. Return ? Invoke(calendar, "weekOfYear", « dateLike »).
+    return calendar.invoke(vm.names.weekOfYear, &date_like);
+}
+
 // 12.1.21 ToTemporalCalendar ( temporalCalendarLike ), https://tc39.es/proposal-temporal/#sec-temporal-totemporalcalendar
 Object* to_temporal_calendar(GlobalObject& global_object, Value temporal_calendar_like)
 {
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
index 6d13bf6d6e4..2471ae37270 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/Calendar.h
@@ -40,6 +40,7 @@ String calendar_month_code(GlobalObject&, Object& calendar, Object& date_like);
 double calendar_day(GlobalObject&, Object& calendar, Object& date_like);
 Value calendar_day_of_week(GlobalObject&, Object& calendar, Object& date_like);
 Value calendar_day_of_year(GlobalObject&, Object& calendar, Object& date_like);
+Value calendar_week_of_year(GlobalObject&, Object& calendar, Object& date_like);
 Object* to_temporal_calendar(GlobalObject&, Value);
 Object* to_temporal_calendar_with_iso_default(GlobalObject&, Value);
 Object* get_temporal_calendar_with_iso_default(GlobalObject&, Object&);
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDatePrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDatePrototype.cpp
index faf027bb3a4..f81984f31f2 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDatePrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDatePrototype.cpp
@@ -33,6 +33,7 @@ void PlainDatePrototype::initialize(GlobalObject& global_object)
     define_native_accessor(vm.names.day, day_getter, {}, Attribute::Configurable);
     define_native_accessor(vm.names.dayOfWeek, day_of_week_getter, {}, Attribute::Configurable);
     define_native_accessor(vm.names.dayOfYear, day_of_year_getter, {}, Attribute::Configurable);
+    define_native_accessor(vm.names.weekOfYear, week_of_year_getter, {}, Attribute::Configurable);
 
     u8 attr = Attribute::Writable | Attribute::Configurable;
     define_native_function(vm.names.withCalendar, with_calendar, 1, attr);
@@ -162,6 +163,22 @@ JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::day_of_year_getter)
     return Value(calendar_day_of_year(global_object, calendar, *temporal_date));
 }
 
+// 3.3.10 get Temporal.PlainDate.prototype.weekOfYear, https://tc39.es/proposal-temporal/#sec-get-temporal.plaindate.prototype.weekofyear
+JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::week_of_year_getter)
+{
+    // 1. Let temporalDate be the this value.
+    // 2. Perform ? RequireInternalSlot(temporalDate, [[InitializedTemporalDate]]).
+    auto* temporal_date = typed_this(global_object);
+    if (vm.exception())
+        return {};
+
+    // 3. Let calendar be temporalDate.[[Calendar]].
+    auto& calendar = temporal_date->calendar();
+
+    // Return ? CalendarWeekOfYear(calendar, temporalDate).
+    return Value(calendar_week_of_year(global_object, calendar, *temporal_date));
+}
+
 // 3.3.22 Temporal.PlainDate.prototype.withCalendar ( calendar ), https://tc39.es/proposal-temporal/#sec-temporal.plaindate.prototype.withcalendar
 JS_DEFINE_NATIVE_FUNCTION(PlainDatePrototype::with_calendar)
 {
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDatePrototype.h b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDatePrototype.h
index c15bcc5d021..e7beffa25e7 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDatePrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDatePrototype.h
@@ -26,6 +26,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(day_getter);
     JS_DECLARE_NATIVE_FUNCTION(day_of_week_getter);
     JS_DECLARE_NATIVE_FUNCTION(day_of_year_getter);
+    JS_DECLARE_NATIVE_FUNCTION(week_of_year_getter);
 
     JS_DECLARE_NATIVE_FUNCTION(with_calendar);
     JS_DECLARE_NATIVE_FUNCTION(equals);
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.prototype.weekOfYear.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.prototype.weekOfYear.js
new file mode 100644
index 00000000000..f0bdbfb0568
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDate/PlainDate.prototype.weekOfYear.js
@@ -0,0 +1,14 @@
+describe("correct behavior", () => {
+    test("basic functionality", () => {
+        const date = new Temporal.PlainDate(2021, 7, 23);
+        expect(date.weekOfYear).toBe(29);
+    });
+});
+
+test("errors", () => {
+    test("this value must be a Temporal.PlainDate object", () => {
+        expect(() => {
+            Reflect.get(Temporal.PlainDate.prototype, "weekOfYear", "foo");
+        }).toThrowWithMessage(TypeError, "Not a Temporal.PlainDate");
+    });
+});