diff --git a/Lib/test/test_types.py b/Lib/test/test_types.py
--- a/Lib/test/test_types.py
+++ b/Lib/test/test_types.py
@@ -2,6 +2,7 @@
 
 from test.support import run_unittest, run_with_locale
 import collections
+import weakref
 import locale
 import sys
 import types
@@ -1135,6 +1136,14 @@
         with self.assertRaises(TypeError):
             ns['spam']
 
+    def test_weakref(self):
+        ns1 = types.SimpleNamespace()
+        ns2 = types.SimpleNamespace()
+        ns2_proxy = weakref.proxy(ns2)
+
+        self.assertIsNone(ns1.__weakref__)
+        self.assertEqual(ns2.__weakref__, ns2_proxy)
+
 
 def test_main():
     run_unittest(TypesTests, MappingProxyTests, ClassCreationTests,
diff --git a/Objects/namespaceobject.c b/Objects/namespaceobject.c
--- a/Objects/namespaceobject.c
+++ b/Objects/namespaceobject.c
@@ -7,11 +7,14 @@
 typedef struct {
     PyObject_HEAD
     PyObject *ns_dict;
+    PyObject *ns_weakreflist;
 } _PyNamespaceObject;
 
 
 static PyMemberDef namespace_members[] = {
     {"__dict__", T_OBJECT, offsetof(_PyNamespaceObject, ns_dict), READONLY},
+    {"__weakref__", T_OBJECT, offsetof(_PyNamespaceObject, ns_weakreflist),
+                                                                  READONLY},
     {NULL}
 };
 
@@ -32,6 +35,8 @@
         return NULL;
     }
 
+    ns->ns_weakreflist = NULL;
+
     PyObject_GC_Track(ns);
     return (PyObject *)ns;
 }
@@ -59,6 +64,9 @@
 static void
 namespace_dealloc(_PyNamespaceObject *ns)
 {
+    if (ns->ns_weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *)ns);
+
     PyObject_GC_UnTrack(ns);
     Py_CLEAR(ns->ns_dict);
     Py_TYPE(ns)->tp_free((PyObject *)ns);
@@ -165,45 +173,45 @@
 
 PyTypeObject _PyNamespace_Type = {
     PyVarObject_HEAD_INIT(&PyType_Type, 0)
-    "namespace",                                /* tp_name */
-    sizeof(_PyNamespaceObject),                 /* tp_size */
-    0,                                          /* tp_itemsize */
-    (destructor)namespace_dealloc,              /* tp_dealloc */
-    0,                                          /* tp_print */
-    0,                                          /* tp_getattr */
-    0,                                          /* tp_setattr */
-    0,                                          /* tp_reserved */
-    (reprfunc)namespace_repr,                   /* tp_repr */
-    0,                                          /* tp_as_number */
-    0,                                          /* tp_as_sequence */
-    0,                                          /* tp_as_mapping */
-    0,                                          /* tp_hash */
-    0,                                          /* tp_call */
-    0,                                          /* tp_str */
-    PyObject_GenericGetAttr,                    /* tp_getattro */
-    PyObject_GenericSetAttr,                    /* tp_setattro */
-    0,                                          /* tp_as_buffer */
+    "namespace",                                  /* tp_name */
+    sizeof(_PyNamespaceObject),                   /* tp_size */
+    0,                                            /* tp_itemsize */
+    (destructor)namespace_dealloc,                /* tp_dealloc */
+    0,                                            /* tp_print */
+    0,                                            /* tp_getattr */
+    0,                                            /* tp_setattr */
+    0,                                            /* tp_reserved */
+    (reprfunc)namespace_repr,                     /* tp_repr */
+    0,                                            /* tp_as_number */
+    0,                                            /* tp_as_sequence */
+    0,                                            /* tp_as_mapping */
+    0,                                            /* tp_hash */
+    0,                                            /* tp_call */
+    0,                                            /* tp_str */
+    PyObject_GenericGetAttr,                      /* tp_getattro */
+    PyObject_GenericSetAttr,                      /* tp_setattro */
+    0,                                            /* tp_as_buffer */
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
-        Py_TPFLAGS_BASETYPE,                    /* tp_flags */
-    namespace_doc,                              /* tp_doc */
-    (traverseproc)namespace_traverse,           /* tp_traverse */
-    (inquiry)namespace_clear,                   /* tp_clear */
-    0,                                          /* tp_richcompare */
-    0,                                          /* tp_weaklistoffset */
-    0,                                          /* tp_iter */
-    0,                                          /* tp_iternext */
-    0,                                          /* tp_methods */
-    namespace_members,                          /* tp_members */
-    0,                                          /* tp_getset */
-    0,                                          /* tp_base */
-    0,                                          /* tp_dict */
-    0,                                          /* tp_descr_get */
-    0,                                          /* tp_descr_set */
-    offsetof(_PyNamespaceObject, ns_dict),      /* tp_dictoffset */
-    (initproc)namespace_init,                   /* tp_init */
-    PyType_GenericAlloc,                        /* tp_alloc */
-    (newfunc)namespace_new,                     /* tp_new */
-    PyObject_GC_Del,                            /* tp_free */
+        Py_TPFLAGS_BASETYPE,                      /* tp_flags */
+    namespace_doc,                                /* tp_doc */
+    (traverseproc)namespace_traverse,             /* tp_traverse */
+    (inquiry)namespace_clear,                     /* tp_clear */
+    0,                                            /* tp_richcompare */
+    offsetof(_PyNamespaceObject, ns_weakreflist), /* tp_weaklistoffset */
+    0,                                            /* tp_iter */
+    0,                                            /* tp_iternext */
+    0,                                            /* tp_methods */
+    namespace_members,                            /* tp_members */
+    0,                                            /* tp_getset */
+    0,                                            /* tp_base */
+    0,                                            /* tp_dict */
+    0,                                            /* tp_descr_get */
+    0,                                            /* tp_descr_set */
+    offsetof(_PyNamespaceObject, ns_dict),        /* tp_dictoffset */
+    (initproc)namespace_init,                     /* tp_init */
+    PyType_GenericAlloc,                          /* tp_alloc */
+    (newfunc)namespace_new,                       /* tp_new */
+    PyObject_GC_Del,                              /* tp_free */
 };