Gustav Carl Friedrich Müller (born 1865 in Germany - date of death unknown; in Rotterdam, Netherlands) was a German bigamist, murderer and self-confessed serial killer. When he surrendered himself to the police, Müller confessed to killing his wife and son, as well as his parents and other wives around the world. Only the murders of his wife and son were proven, but taking his insanity into consideration, Müller was acquitted by reason of insanity and sent off to a mental institution, where he presumably died.