Robert Edward Crosby (born January 12, 1980, in Lakewood, California) is an infielder in Major League Baseball who is currently a free agent. The son of former major league infielder Ed Crosby, he bats and throws right-handed. He was Rookie of the Year in 2004.

Crosby first attended Pacifica High School, and then later graduated from La Quinta High School in Westminster, California. In 1998, Bobby Crosby was selected by the Anaheim Angels in the thirty-fourth round of the Major League Baseball Draft. Crosby chose not to sign with the Angels, however, opting instead to play college baseball for California State University, Long Beach. In 2001, Crosby was selected by the Oakland Athletics in the first round (25th pick) of the Major League Baseball Draft.

In 2004, his first full season, he took over the Athletics' shortstop duties from 2002 American League Most Valuable Player Miguel Tejada, who signed with the Baltimore Orioles as a free agent. That year, Crosby hit .239 with 22 home runs and 64 RBIs. He also led American League rookies in hits (130), doubles (34) and walks (58). These numbers earned Crosby Rookie of the Year honors, the sixth Athletics player to do so after Harry Byrd (1952), José Canseco (1986), Mark McGwire (1987), Walt Weiss (1988), and Ben Grieve (1998).