Steven Robert Ontiveros (born October 26, 1951) is a former third baseman in Major League Baseball who played from 1973 through 1980 for the San Francisco Giants (1973–1976) and Chicago Cubs (1977–1980). He also played six seasons in Japan for the Seibu Lions (1980–1985). Ontiveros was a switch-hitter and threw right-handed. He is of Mexican American descent. In an eight-season career, Ontiveros was a .274 hitter with 24 home runs and 224 RBI in 732 games. Following his majors career, he played in Japan with the Seibu Lions from 1980 to 1985 and hit .312 with 82 home runs and 390 RBI.