The younger Watt announced his decision to enter the draft on his Twitter account Tuesday.
"This season has been an absolute blast," Watt wrote. "I could not have asked for a better group of guys to play with, better coaches to play for, or a better fan base to represent."
"Playing for the University of Wisconsin has always been a dream of mine and I am extremely fortunate to have been able to fulfill that dream."
"... This decision was by no means an easy one, but I feel that it is the right decision for me at this time."
Watt, 22, led the Badgers (11-3) with 11 1/2 sacks and totaled 63 tackles with 15 1/2 stops for a loss and two forced fumbles.
ESPN's Mel Kiper Jr. ranks Watt as the 10th-best outside linebacker in this year's draft class.