Gary Joseph Gaetti (pronounced /ˈɡaɪ.ɛti/; born August 19, 1958 in Centralia, Illinois), nicknamed "G-Man" ("Rat" or "Zorn" during his earlier days), is an American former third baseman in Major League Baseball for the Minnesota Twins (1981-90), California Angels (1991-93), Kansas City Royals (1993-95), St. Louis Cardinals (1996-98), Chicago Cubs (1998-99) and Boston Red Sox (2000).

Gaetti won a World Series championship with Minnesota in 1987 and was the MVP of that year's American League Championship Series against the Detroit Tigers. That year, he became the first player ever to hit home runs in his first two postseason plate appearances: in 2008, Evan Longoria became the second.

Gaetti won four Gold Glove Awards for fielding excellence from 1986 through 1989, and was selected an All-Star in 1988 and 1989. A power-hitting third baseman who had his best season in 1986 when he batted .287 with 34 home runs and 108 runs batted in, Gaetti left the Twins for the Angels as a free agent following the 1990 season. His production dropped significantly with the Angels, who released him in June 1993. He signed with the Royals, who had lost their projected regular third baseman, Keith Miller, to injury, and had been playing struggling rookie Phil Hiatt at third. Handed the third base job, Gaetti turned his career around. In 1995, at the age of 36, he put together one of his best seasons, hitting .261/35/96, setting a career high in home runs and missing the Royals team record for most home runs in a season by one.