diff --git a/Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h b/Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h
index a2bbf9e2b1..852d089f4b 100644
--- a/Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h
+++ b/Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h
@@ -13,6 +13,8 @@ namespace JS {
 
 #define ENUMERATE_STANDARD_PROPERTY_NAMES(P) \
     P(__proto__)                             \
+    P(__defineGetter__)                      \
+    P(__defineSetter__)                      \
     P(BYTES_PER_ELEMENT)                     \
     P(BigInt)                                \
     P(Boolean)                               \
diff --git a/Userland/Libraries/LibJS/Runtime/ObjectPrototype.cpp b/Userland/Libraries/LibJS/Runtime/ObjectPrototype.cpp
index 97e2049c36..87c16d533c 100644
--- a/Userland/Libraries/LibJS/Runtime/ObjectPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/ObjectPrototype.cpp
@@ -6,6 +6,7 @@
 
 #include <AK/Function.h>
 #include <AK/String.h>
+#include <LibJS/Runtime/Accessor.h>
 #include <LibJS/Runtime/BooleanObject.h>
 #include <LibJS/Runtime/Date.h>
 #include <LibJS/Runtime/GlobalObject.h>
@@ -37,6 +38,8 @@ void ObjectPrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.isPrototypeOf, is_prototype_of, 1, attr);
 
     // Annex B
+    define_native_function(vm.names.__defineGetter__, define_getter, 2, attr);
+    define_native_function(vm.names.__defineSetter__, define_setter, 2, attr);
     define_native_accessor(vm.names.__proto__, proto_getter, proto_setter, Attribute::Configurable);
 }
 
@@ -147,6 +150,70 @@ JS_DEFINE_NATIVE_FUNCTION(ObjectPrototype::is_prototype_of)
     }
 }
 
+// B.2.2.2 Object.prototype.__defineGetter__ ( P, getter ), https://tc39.es/ecma262/#sec-object.prototype.__defineGetter__
+JS_DEFINE_NATIVE_FUNCTION(ObjectPrototype::define_getter)
+{
+    auto object = vm.this_value(global_object).to_object(global_object);
+    if (vm.exception())
+        return {};
+
+    auto getter = vm.argument(1);
+    if (!getter.is_function()) {
+        vm.throw_exception<TypeError>(global_object, ErrorType::NotAFunction, getter.to_string_without_side_effects());
+        return {};
+    }
+
+    auto key = vm.argument(0).to_property_key(global_object);
+    if (vm.exception())
+        return {};
+
+    auto descriptor = Object::create(global_object, global_object.object_prototype());
+    descriptor->define_property(vm.names.get, getter);
+    descriptor->define_property(vm.names.enumerable, Value(true));
+    descriptor->define_property(vm.names.configurable, Value(true));
+
+    auto success = object->define_property(key, *descriptor);
+    if (vm.exception())
+        return {};
+    if (!success) {
+        vm.throw_exception<TypeError>(global_object, ErrorType::ObjectDefinePropertyReturnedFalse);
+        return {};
+    }
+    return js_undefined();
+}
+
+// B.2.2.3 Object.prototype.__defineSetter__ ( P, getter ), https://tc39.es/ecma262/#sec-object.prototype.__defineSetter__
+JS_DEFINE_NATIVE_FUNCTION(ObjectPrototype::define_setter)
+{
+    auto object = vm.this_value(global_object).to_object(global_object);
+    if (vm.exception())
+        return {};
+
+    auto setter = vm.argument(1);
+    if (!setter.is_function()) {
+        vm.throw_exception<TypeError>(global_object, ErrorType::NotAFunction, setter.to_string_without_side_effects());
+        return {};
+    }
+
+    auto key = vm.argument(0).to_property_key(global_object);
+    if (vm.exception())
+        return {};
+
+    auto descriptor = Object::create(global_object, global_object.object_prototype());
+    descriptor->define_property(vm.names.set, setter);
+    descriptor->define_property(vm.names.enumerable, Value(true));
+    descriptor->define_property(vm.names.configurable, Value(true));
+
+    auto success = object->define_property(key, *descriptor);
+    if (vm.exception())
+        return {};
+    if (!success) {
+        vm.throw_exception<TypeError>(global_object, ErrorType::ObjectDefinePropertyReturnedFalse);
+        return {};
+    }
+    return js_undefined();
+}
+
 // B.2.2.1.1 get Object.prototype.__proto__, https://tc39.es/ecma262/#sec-get-object.prototype.__proto__
 JS_DEFINE_NATIVE_FUNCTION(ObjectPrototype::proto_getter)
 {
diff --git a/Userland/Libraries/LibJS/Runtime/ObjectPrototype.h b/Userland/Libraries/LibJS/Runtime/ObjectPrototype.h
index b01208a93b..83f41f8f0f 100644
--- a/Userland/Libraries/LibJS/Runtime/ObjectPrototype.h
+++ b/Userland/Libraries/LibJS/Runtime/ObjectPrototype.h
@@ -27,6 +27,8 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(value_of);
     JS_DECLARE_NATIVE_FUNCTION(property_is_enumerable);
     JS_DECLARE_NATIVE_FUNCTION(is_prototype_of);
+    JS_DECLARE_NATIVE_FUNCTION(define_getter);
+    JS_DECLARE_NATIVE_FUNCTION(define_setter);
     JS_DECLARE_NATIVE_FUNCTION(proto_getter);
     JS_DECLARE_NATIVE_FUNCTION(proto_setter);
 };