Alt is a surname. Notable people with the surname include:
Albrecht Alt (1883–1956), German bible scholar and Protestant theologianCarol Alt (born 1960), American model and actressErnst Alt, German Roman Catholic priest and exorcistFranz Alt (mathematician) (1910–2011), Austrian-born American mathematicianFranz Alt (painter) (1821–1914), Austrian painter, brother of RudolfRudolf von Alt (1812–1905), Austrian painterSalome Alt (1568–1633), Austrian wife of Wolf Dietrich (von) RaitenauSusanne Alt (born 1978), German female saxophonist