Kalen Bruce Thornton (born May 12, 1982 in Dallas, Texas) is a former American football linebacker for the Dallas Cowboys of the National Football League. He played in fifteen games in the 2004 season but was forced to retire in 2006 after missing part of the 2005 season because of a knee injury. Following his professional football career, Thornton spent time in private wealth management for Morgan Stanley Smith Barney until 2009 and now is a student at Stanford Graduate School of Business. Thornton graduated from St. Mark's School of Texas. He played college football for the University of Texas at Austin, where he was an All-Conference defensive end as well as an Academic All-Conference student-athlete.