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. On April 17, 1977, Ontiveros singled against the New York Mets' Tom Seaver, in Seaver's fifth career one-hit game.