Johnathan Mackensey "Mac" Williamson (born July 15, 1990) is an American professional baseball outfielder in the Washington Nationals organization.
He played college baseball at Wake Forest University.
In the 2012 MLB Draft, the San Francisco Giants selected Williamson in the third round, with the 115th overall selection. He signed with the Giants, beginning his professional career in the Rookie-level Arizona League.
Williamson made his MLB debut September 23, 2015, for the San Francisco.
On January 15, 2020, Williamson signed a minor league deal with the Washington Nationals.