Gary Joseph Gaetti, is an American former third baseman in Major League Baseball for the Minnesota Twins (1981–1990), California Angels (1991–1993), Kansas City Royals (1993–1995), St. Louis Cardinals (1996–1998), Chicago Cubs (1998–1999) and Boston Red Sox (2000).

A third baseman, abbreviated 3B, is the player in baseball or softball whose responsibility is to defend the area nearest to third base — the third of four bases a baserunner must touch in succession to score a run. In the scoring system used to record defensive plays, the third baseman is assigned the number 5.