Lemass is a surname. Notable people with the surname include:
Eileen Lemass (born 1932), Irish politician, wife of Noel Kathleen Lemass (1898–1985), wife of Seán Lemass Maureen Lemass, the birth name of Maureen Haughey (1925–2017), wife of Taoiseach Charles Haughey Noel Lemass (1929–1976), Irish politician Seán Lemass (1899–1971), Irish head of government Lemass era, a period of economic change between 1959 and 1966