Derek Anthony Barnett is an American football defensive end. He played college football at Tennessee.

Barnett attended Brentwood Academy in Brentwood, Tennessee. As a senior, he had 60 tackles (18 for loss) and 5.5 sacks. He was rated by Rivals.com as a four-star recruit. In 2013, he committed to the University of Tennessee to play college football.

Barnett became the first true freshman defensive lineman to start the season opener in Tennessee history. Overall, he played in all 13 games and made 10 starts. He finished the season with school true freshman records of 10 sacks and 20.5 tackles for loss. Both Barnett and Myles Garrett broke Jadeveon Clowney's SEC freshman sack record, which had previously been 8.0. On December 30, 2016, in the 2016 Music City Bowl, Barnett broke the University of Tennessee's career sack record of 32.0, which was formerly held by Reggie White.