William Harlan Haas is an American professional golfer who plays on the PGA Tour and won the 2011 FedEx Cup. He is the son of former PGA Tour player Jay Haas.

In his debut year on tour, Haas finished 99th on the money list, making 19 out of 30 cuts. His best result was at the Wachovia Championship where he finished in a tie for fourth.

Haas was a member of the Nationwide Tour (now Web.com Tour) in 2005 after failing to earn his PGA Tour card in qualifying school. His best finish in a Nationwide Tour event was a solo second at the 2005 Scholarship America Showdown. At the end of the season, Haas birdied the last two holes at the 2005 qualifying tournament to earn his card on the PGA Tour for the 2006 season.

Bill Haas siblings: Meet his brother Jay Haas Jr.

Haas comes from a distinguished family of golfers. His father is a nine-time PGA Tour winner, Jay Haas. His brother, Jay Haas Jr., and uncle, Jerry Haas, are former PGA Tour players. He is a great nephew of 1968 Masters Tournament winner, Bob Goalby.