Dennis Sullivan (born 1941) is an American mathematician.
Dennis Sullivan may also refer to:
- Dennis Sullivan (cricketer) (1883–1968), English cricketer
- Dennis B. Sullivan (1927–2020), U.S. Air Force general
- Dennis Joseph Sullivan (born 1945), American prelate of the Roman Catholic Church
- Dennis Mark Sullivan (1841-1917), American businessman and politician
- Dennis Michael Sullivan, American electrical engineer
- Dennis T. Sullivan (died 1906), American Chief of the San Francisco Fire Department in 1906
- Dennis Sullivan, producer of Pork, a political talk show on the America's Talking network