Sainz is a surname. Notable people with the surname include:
Adolfo Fernández Sainz (born 1947), Cuban journalist
Bernard Sainz (born 1943), unlicensed sports doctor who achieved success in horse racing and cycling
Carlos Sainz (born 1962), Spanish rally driver
Carlos Sainz Jr. (born 1994), Spanish racing driver, son of Carlos Sainz
Faustino Sainz Muñoz (born 1937), Spanish prelate of the Roman Catholic Church
Gustavo Sainz (born 1940), Spanish language author from Mexico
Inés Sainz (born 1978), Mexican journalist
Inés Sáinz Esteban, Spanish beauty pageant
José Sáinz Nothnagel (1907–1984), Falangist, early leader Spanish Civil War
Lolo Sainz (born 1940), Spanish former basketball player and coach
Regino Sainz de la Maza (1896–1981), Spanish classical guitarist
Severiano Sainz y Bencamo (1871–1937), the second Bishop of the Roman Catholic Diocese of Matanzas (1915–1937)