William Fred “Billy” Mayfair (born August 6, 1966) is an American PGA Tour golfer.

Mayfair was born in Phoenix, Arizona, and now lives in Scottsdale, Arizona where he plays out of Estrella Mountain Range Golf Club. He went to Arizona State University and won the 1986 U.S. Amateur Public Links and the 1987 U.S. Amateur Championship.

On July 31, 2006, Mayfair was diagnosed with testicular cancer. He had surgery on August 3 and it has been reported that the cancer was contained.

Professional career
Mayfair turned professional in 1988 and has won five events on the PGA Tour, including the 1995 Tour Championship. He has featured in the top 50 of the Official World Golf Rankings. He holds the distinction of being the only player to ever beat Tiger Woods in a playoff on the PGA Tour (1998 Nissan Open).

Amateur wins
1987 Pacific Coast Amateur
1988 Pacific Coast Amateur

PGA Tour wins (5)
1993 (1) Greater Milwaukee Open
1995 (2) Motorola Western Open, The Tour Championship
1998 (2) Nissan Open, Buick Open