S.M., also sometimes referred to as SM-046, is an American woman with a peculiar type of brain damage that prevents her from experiencing fear. First described by scientists in 1994, she has had exclusive and complete bilateral amygdala destruction since late childhood as a consequence of Urbach–Wiethe disease. Dubbed by the media as the "woman with no fear", S.M. has been studied extensively in scientific research; she has helped researchers elucidate the function of the amygdala.