diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
index 3a68713a6e..92b82db723 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.cpp
@@ -64,6 +64,7 @@ void PlainDateTimePrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.subtract, subtract, 1, attr);
     define_native_function(vm.names.equals, equals, 1, attr);
     define_native_function(vm.names.toString, to_string, 0, attr);
+    define_native_function(vm.names.toLocaleString, to_locale_string, 0, attr);
     define_native_function(vm.names.valueOf, value_of, 0, attr);
     define_native_function(vm.names.toZonedDateTime, to_zoned_date_time, 1, attr);
     define_native_function(vm.names.toPlainDate, to_plain_date, 0, attr);
@@ -496,6 +497,18 @@ JS_DEFINE_NATIVE_FUNCTION(PlainDateTimePrototype::to_string)
     return js_string(vm, TRY(temporal_date_time_to_string(global_object, result.year, result.month, result.day, result.hour, result.minute, result.second, result.millisecond, result.microsecond, result.nanosecond, &date_time->calendar(), precision.precision, show_calendar)));
 }
 
+// 5.3.33 Temporal.PlainDateTime.prototype.toLocaleString ( [ locales [ , options ] ] ), https://tc39.es/proposal-temporal/#sec-temporal.plaindatetime.prototype.tolocalestring
+// NOTE: This is the minimum toLocaleString implementation for engines without ECMA-402.
+JS_DEFINE_NATIVE_FUNCTION(PlainDateTimePrototype::to_locale_string)
+{
+    // 1. Let dateTime be the this value.
+    // 2. Perform ? RequireInternalSlot(dateTime, [[InitializedTemporalDateTime]]).
+    auto* date_time = TRY(typed_this_object(global_object));
+
+    // 3. Return ? TemporalDateTimeToString(dateTime.[[ISOYear]], dateTime.[[ISOMonth]], dateTime.[[ISODay]], dateTime.[[ISOHour]], dateTime.[[ISOMinute]], dateTime.[[ISOSecond]], dateTime.[[ISOMillisecond]], dateTime.[[ISOMicrosecond]], dateTime.[[ISONanosecond]], dateTime.[[Calendar]], "auto", "auto").
+    return js_string(vm, TRY(temporal_date_time_to_string(global_object, date_time->iso_year(), date_time->iso_month(), date_time->iso_day(), date_time->iso_hour(), date_time->iso_minute(), date_time->iso_second(), date_time->iso_millisecond(), date_time->iso_microsecond(), date_time->iso_nanosecond(), &date_time->calendar(), "auto"sv, "auto"sv)));
+}
+
 // 5.3.35 Temporal.PlainDateTime.prototype.valueOf ( ), https://tc39.es/proposal-temporal/#sec-temporal.plaindatetime.prototype.valueof
 JS_DEFINE_NATIVE_FUNCTION(PlainDateTimePrototype::value_of)
 {
diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
index cdc032d731..f10b7a6677 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainDateTimePrototype.h
@@ -48,6 +48,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(subtract);
     JS_DECLARE_NATIVE_FUNCTION(equals);
     JS_DECLARE_NATIVE_FUNCTION(to_string);
+    JS_DECLARE_NATIVE_FUNCTION(to_locale_string);
     JS_DECLARE_NATIVE_FUNCTION(value_of);
     JS_DECLARE_NATIVE_FUNCTION(to_zoned_date_time);
     JS_DECLARE_NATIVE_FUNCTION(to_plain_date);
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.toLocaleString.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.toLocaleString.js
new file mode 100644
index 0000000000..1f35fa767f
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainDateTime/PlainDateTime.prototype.toLocaleString.js
@@ -0,0 +1,18 @@
+describe("correct behavior", () => {
+    test("length is 0", () => {
+        expect(Temporal.PlainDateTime.prototype.toLocaleString).toHaveLength(0);
+    });
+
+    test("basic functionality", () => {
+        const plainDateTime = new Temporal.PlainDateTime(2021, 11, 3, 1, 33, 5, 100, 200, 300);
+        expect(plainDateTime.toLocaleString()).toBe("2021-11-03T01:33:05.1002003");
+    });
+});
+
+describe("errors", () => {
+    test("this value must be a Temporal.PlainDateTime object", () => {
+        expect(() => {
+            Temporal.PlainDateTime.prototype.toLocaleString.call("foo");
+        }).toThrowWithMessage(TypeError, "Not an object of type Temporal.PlainDateTime");
+    });
+});