McIlwain is a surname. Notable people with the surname include:
Alfie McIlwain (born 1998), English actor Charles Howard McIlwain (1871–1968), American historian and political scientist Dallas McIlwain (born 1982), Australian rugby league player David McIlwain (1921–1981), English science fiction writer Douglas McIlwain (born 1968), English local politician Mayor of Huntingdon James McIlwain, American ophthalmologist Serena McIlwain, American government official Stover McIlwain (1939–1966), American baseball player Wally McIlwain (1903–1963), American football player Zach McIlwain (1986–2024), American national veterans advocate