Melvin Emanuel "B.J." Upton (born August 21, 1984 in Norfolk, Virginia) is a Major League Baseball center fielder for the Tampa Bay Rays. His nickname, B.J., is short for "Bossman Junior" - his father's nickname was "Bossman." Upton was drafted second overall in the 2002 Major League Baseball Draft by Tampa Bay out of Greenbrier Christian Academy in Chesapeake, Virginia. Widely considered a very polished prospect able to hit for both power and average, poor defensive play at shortstop kept him in the minor leagues until 2007.

As a member of the 2001 Team USA Junior National team, Upton batted .462 (12-for-26) in nine games. The team went 9-2 and won the Silver Medal in Cuba that year. In 2002, Upton was named a first-team All-American by Baseball America, batting .641 (50-for-78) with 11 doubles, 4 triples, 11 home runs and 32 RBI during his senior year at Greenbrier.

In 2003, Upton committed 56 errors, leading the minor leagues. He was ranked as the #21 prospect in baseball that year by Baseball America, and as the #2 prospect a year later in 2004. He made his major league debut on August 2, 2004, becoming the youngest Devil Ray ever and the youngest player in the major leagues in 2004. In that game against the Boston Red Sox, he went 1-3 with a walk, with his hit being a seventh-inning single off Tim Wakefield. His younger brother, Justin, was taken with the top overall choice of the 2005 Major League Baseball Draft, making them the highest-drafted siblings of all time. Upton was the starting shortstop in both the 2004 and 2005 All-Star Futures Games.

In 2007, Upton emerged from spring training as the Rays' starting second baseman. On June 8, Upton was forced to leave a game against the Florida Marlins early due to a strained left quadricep. The injury forced him out of action until July 13. Before the injury, he was batting .320/.396/.545 with 9 home runs. Although he played mostly second base until the injury, Upton has been the team's starting center fielder since returning.

In 2007, he had 24 home runs, and was 22-8 in stolen base attempts. He was one of only 6 batters in the AL to have at least 20 home runs and 20 stolen bases, along with Alex Rodriguez, Gary Sheffield, Ian Kinsler, Grady Sizemore, and Curtis Granderson.