Josh Byrnes is the former General Manager of the Arizona Diamondbacks of Major League Baseball, serving as GM from November 2005 to July 2010.
Byrnes grew up in Washington, D.C., where he attended and played second base for St. Albans School. He graduated in 1992 from Haverford College with a BA in English. He played on the collegiate baseball team with at Haverford. He began his professional career with a health-care consulting company after school. He began his baseball career for the Cleveland Indians in 1994, quickly working his way up the organizational ladder, first as an intern, then as a video scout, and, eventually, to the position of scouting director in 1998. In 1999, he was hired by colleague Dan O'Dowd to fill the assistant GM position for the Colorado Rockies, a job he held for two years. He then took the same job under Theo Epstein and the Boston Red Sox until October 2005, when he was hired by the Diamondbacks to replace the departing interim General Manager Bob Gebhard.
Part of the new breed of young general managers, Byrnes was 35 when he was hired by the Diamondbacks in 2005. In February 2008, he was given an 8-year extension that was to last through the 2015 season.