Ngô Đồng (born South Vietnam - died 15 May 2000), known also by the Japanese title O Sensei, was a Vietnam-born naturalised American entomologist and martial arts instructor. He is chiefly known as the founder and grandmaster of the international school of Cuong Nhu Oriental Martial Arts. Having served as a college president in South Vietnam before the fall of Saigon in 1975, he spent time in a re-education camp until escaping in a small boat. He taught entomology at the University of Florida for the remainder of his career, guiding the international Cuong Nhu martial arts community at the same time.