Butler, seeded eighth in the Southeast Region, narrowly missed defeating Duke in last year's championship game, but another trip to the Final Four seemed unlikely after the Bulldogs lost five times in the Horizon League's regular season.
They won their league tournament, however, and have defeated Old Dominion, top-seeded Pittsburgh and fourth-seeded Wisconsin to reach the regional finals. Butler will go after its second straight Final Four trip Saturday when it takes on second-seeded Florida, an overtime winner earlier in the evening over BYU.
Howard hit 9-of-10 from the foul line while scoring 20 points and was part of a defensive effort that limited Wisconsin to 17 field goals for the entire game.
The Bulldogs built a 20-point lead by holding Wisconsin without a point for the final 2 minutes of the opening period and the first 4:24 of the second.
Wisconsin rallied to within four points with 30 seconds remaining on Jordan Taylor's 3-pointer, but the Badgers did little right the rest of the way.
Shelvin Mack made a free throw for Butler to extend the lead to five points and when he missed the second try, Howard was there for an offensive rebound. Howard then made two foul shots with 29 seconds left and Taylor turned the ball over to end Wisconsin's hopes.
Mack added 13 points for Butler (27-9). Taylor was the only player to reach double digits for Wisconsin (25-8) with 22.