Rex Daniel Grossman III (born August 23, 1980) is a former American football quarterback who played in the National Football League (NFL) for 11 seasons, most notably with the Chicago Bears. He played college football at Florida, where he received consensus All-America honors and made three bowl game appearances, winning the 2002 Orange Bowl. Grossman was selected by the Bears in the first round of the 2003 NFL Draft.

After struggling with injuries during his first three years, Grossman had his most successful season in 2006 when he helped lead the Bears to a Super Bowl appearance in Super Bowl XLI. Due to inconsistent play, however, Grossman lost his starter role the following season. He spent the remainder of his career mostly as a backup, holding his last starting position with the Washington Redskins in 2011.