Mark Duffner (born July 19, 1953) is an American football coach who is currently a senior defensive assistant for the Cincinnati Bengals of the National Football League (NFL). Duffner served as the head coach of the Maryland Terrapins football team from 1992 to 1996. Duffner was hired by the Bengals as a senior defensive assistant on March 7, 2019. He missed the team's week 10 game in 2020 against the Pittsburgh Steelers due to COVID-19 pandemic protocols.