Mac Cassin (born July 19, 1991) is a former national champion racing cyclist from the United States.

While attending the University of Colorado Boulder he won 5 Collegiate National Titles on the track between 2011 and 2015 (3 Individual Pursuit, 1 Points Race, 1 Omnium).

After taking a solo win at the Glencoe Grand Prix in 2015 he was offered a spot on Champion Systems p/b Stan's No Tubes to ride the men's team time trial at the 2015 UCI Road World Championships.

After undergoing back surgery in March 2016 he was named to the US National Team for the 2016 Pan American Track Cycling Championships where he competed in the Individual Pursuit and Points Race.

In 2017, Cassin was crowned the US National Points Race Champion after placing second in both the Team Pursuit and Individual Pursuit.