diff --git a/mypy/checker.py b/mypy/checker.py
index 9c389cccd95f..3c132731d809 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -3078,6 +3078,11 @@ def visit_assignment_stmt(self, s: AssignmentStmt) -> None:
             with self.enter_final_context(s.is_final_def):
                 self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None, s.new_syntax)
 
+        for lv in s.lvalues:
+            if isinstance(lv, MemberExpr):
+                if lv.name == "__class__":
+                    self.fail("Assignment to '__class__' is unsafe and not allowed", lv)
+
         if s.is_alias_def:
             self.check_type_alias_rvalue(s)
 
diff --git a/test-data/unit/check-assign-to-class.test b/test-data/unit/check-assign-to-class.test
new file mode 100644
index 000000000000..53043c657e12
--- /dev/null
+++ b/test-data/unit/check-assign-to-class.test
@@ -0,0 +1,22 @@
+[case test_assign_to_dunder_class]
+class A:
+    def foo(self):
+        self.__class__ = B  # E: Assignment to '__class__' is unsafe and not allowed
+
+class B:
+    pass
+
+[case test_assign_to_other_dunder_attributes]
+class C:
+    def bar(self):
+        self.__name__ = "NewName"  # OK
+        self.__doc__ = "Test doc"  # OK
+
+class D:
+    pass
+
+[case test_assign_to_regular_attribute]
+class E:
+    x = 1
+    def baz(self):
+        self.x = 2  # OK