The Baltimore brand, the official apparel supplier for the 2016 NFL Combine, announced the multi-year deal today.
Under Armour said it singled out Jack as "one of the most dynamic and exciting talents in this year's NFL Draft class."
"Myles demonstrated that he is not only one of the most electric defensive players in college football, but is one of the hardest workers, in training and preparation," Ryan Kuehl, vice president for sports marketing and sponsorships, said in the announcement.
Jack joins an Under Armour roster of football player endorsers that includes three-time NFL MVP Tom Brady, reigning NFL MVP Cam Newton, two-time first team All Pro Patrick Peterson, 2016 All Pro wide receiver Julio Jones and six time Pro Bowler Brandon Marshall.
"Under Armour is an incredible company with a tremendous focus on innovation, which is exactly where I want to be as I start my professional career,” Jack said in the announcement.
The Georgia native was the first player to be named both Offensive and Defensive Freshmen of the Year in the Pac-12 and was a finalist for the 2013 Paul Hornung Award as the nation’s most versatile player. In 2014, Jack finished second on the Bruins with 88 tackles and recorded a 41-yard interception return in their Alamo Bowl victory.