Tremayne is a Cornish language surname. Notable people with the surname include:
Arthur Tremayne (1827–1905), Crimean War soldier and Cornish MP
David Tremayne, British motorcycling journalist
John Claude Lewis Tremayne (1869–1949), last squire of Heligan and better known as "Jack"
John Hearle Tremayne (1780–1851), Cornish MP and High Sheriff of Cornwall in 1831
John Tremayne (of Collacombe), High Sheriff of Cornwall in 1485
John Tremayne (of Tremayne), High Sheriff of Cornwall in 1487
John Tremayne (of Heligan), High Sheriff of Cornwall in 1745
John Tremayne (1825–1901), MP for constituencies in both Cornwall and Devon, and High Sheriff of Cornwall in 1859
Henry Hawkins Tremayne (1741–1829), clergyman and squire of Heligan
Kate Tremayne, British novelist
Peter Tremayne, pseudonym of Peter Berresford Ellis (b. 1943) British biographer, historian, and novelist
Dick Tremayne, character in Twin Peaks
Tremayne, (Anthony Nicholls), a character in The Champions, a British TV series on the UK network ITV during 1968–69
John Tremayne Babington (later John Tremayne Tremayne), British Air Marshal and High Sheriff of Cornwall in 1954
Jorge Tremayne, U.S. Navy 1973–1984