Justin Arch "Jay" Williamson IV (born February 7, 1967) is an American professional golfer who has played on the PGA Tour and the Nationwide Tour.

Williamson was born in St. Louis, Missouri. After graduating from Trinity College, he turned professional in 1990.

Williamson has no PGA Tour victories, although he has finished 2nd twice, both playoff losses - to Hunter Mahan at the 2007 Travelers Championship, and to Kenny Perry at the 2008 John Deere Classic. He won once on the Nationwide Tour: the 2007 Fort Smith Classic. He has more than $5 million in career earnings.