Threlfall is a surname. Notable people with the surname include:
David Threlfall (b. 1953), English actor
Edward Threlfall, English footballer in the early 1900s
George Threlfall (1819–1897), English-born Australian engineer and entrepreneur
Mary Threlfall (1910–1996), Australian nurse
Richard Threlfall (1861–1932), English chemist
Robbie Threlfall (b. 1988), English footballer
T. R. Threlfall, English trade unionist and politician
Wilf Threlfall (1901-??), English footballer
William Threlfall German mathematician
Mhairi Threlfall English politician
