"While I am incredibly excited about the opportunities and challenges that await me," Simmons wrote on social media, "please know that a part of my heart will always remain here in Clemson, South Carolina."
At 6-foot-4, 225 pounds, Simmons has the athleticism and size to play corner, safety and linebacker. He's the No. 1-ranked outside linebacker prospect for April's draft, according to ESPN's Mel Kiper Jr.
The 21-year-old had 8 sacks, 107 tackles, 16 tackles for loss, 10 pass breakups, 3 interceptions and 1 forced fumble in 15 games for Clemson last season.
Simmons had seven tackles, a sack and two passes defended in Clemson's loss to LSU in the College Football Playoff National Championship on Monday.