diff --git a/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonthPrototype.cpp b/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonthPrototype.cpp
index dff105c060..7af2cdf406 100644
--- a/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonthPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/Temporal/PlainYearMonthPrototype.cpp
@@ -18,6 +18,11 @@ PlainYearMonthPrototype::PlainYearMonthPrototype(GlobalObject& global_object)
 void PlainYearMonthPrototype::initialize(GlobalObject& global_object)
 {
     Object::initialize(global_object);
+
+    auto& vm = this->vm();
+
+    // 9.3.2 Temporal.PlainYearMonth.prototype[ @@toStringTag ], https://tc39.es/proposal-temporal/#sec-temporal.plainyearmonth.prototype-@@tostringtag
+    define_direct_property(*vm.well_known_symbol_to_string_tag(), js_string(vm.heap(), "Temporal.PlainYearMonth"), Attribute::Configurable);
 }
 
 }
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainYearMonth/PlainYearMonth.prototype.@@toStringTag.js b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainYearMonth/PlainYearMonth.prototype.@@toStringTag.js
new file mode 100644
index 0000000000..65296d77b2
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Temporal/PlainYearMonth/PlainYearMonth.prototype.@@toStringTag.js
@@ -0,0 +1,3 @@
+test("basic functionality", () => {
+    expect(Temporal.PlainYearMonth.prototype[Symbol.toStringTag]).toBe("Temporal.PlainYearMonth");
+});