Daniel Blain, M.D. (1898–1981) was an American physician and was the first medical director of the American Psychiatric Association (APA), the first professional , founded in the United States in 1844. He may be credited with the leadership which brought changes in the practice of psychiatry after World War II and in advocating the treatment for people with mental disorders. From 1966 to 1970, Blain was the superintendent of Philadelphia State Hospital at Byberry which had a long history of custodial care. He died in Philadelphia in 1981.