Nguyễn Đan Quế, M.D. (born 13 April 1942) is a Vietnamese endocrinologist and pro-democracy activist in Saigon. He was imprisoned from 1978 to 1988, 1990–1998, 2003–2005, and briefly in 2011 on state security charges related to his activism. In 2003, The New York Times described him as "Vietnam's most renowned dissident".