Onions is a surname, also spelled O'Nions. Notable persons with that surname include:
Alfred Onions (1858–1921), Welsh Labour Party politician
Charles Talbut Onions (1873–1965), English grammarian and lexicographer
George Onions (1883–1944), English recipient of the Victoria Cross
Graham Onions (born 1982), English cricketer
Keith O'Nions (born 1944), British scientist, president and rector of Imperial College London
Oliver Onions (1873–1961), English novelist
Sheila O'Nions Walsh (1928–2009), English novelist, also known as Sheila Walsh and Sophie Leyton
