Morgan Paige scored a career-high 33 points to lead Wisconsin to a 63-61 upset over seventh-ranked Penn State.
Tiera Stephens scored the game-winning basket on a putback with 5 seconds left at the Kohl Center for the Badgers, who stopped the Nittany Lions' 11-game winning streak.
Alex Bentley drove the length of the floor and missed a layup at the buzzer for Penn State (17-3, 7-1).
Stephens scored five points and had 11 rebounds and Jacki Gulczynski added 16 for Wisconsin (10-11, 2-6 Big Ten). The victory against a ranked opponent was the Badgers' first since a 48-45 win against No. 20 Michigan State on January 14, 2010.
Maggie Lucas scored 18 points and Mia Nickson added 11 for the Lady Lions, who throttled the Badgers 84-40 at home two weeks ago for their most lopsided victory since 2001.
Wisconsin raced to a 17-6 lead in the first 8 minutes of the game, but Penn State was able to chip away at the lead during a four-minute plus scoring drought. Lucas and Dara Taylor combined for seven points during a 13-0 run that gave Penn State the lead going into the break at 33-29.
Penn State led by as many as seven points early in the second half, but Wisconsin never far behind. With every mini run the Nittany Lions strung together, the Badgers would answer with a key steal or basket.
Wisconsin wrestled the lead back at 55-53 when Gulczynski made a 3-pointer at the top of the key, but Lucas came back on the other end to drain a long-range shot. The teams traded the lead four times with less than four minutes remaining, and Paige provided momentum in the closing minute for Wisconsin.
Paige drilled a deep 3-pointer from 25 feet to give Wisconsin a 61-59 lead with 58 seconds left, but Bentley tied the game at 61 with an off-balance jumper with 27 seconds to go.
The Badgers have relied heavily on Paige's scoring prowess this season. The junior guard, who shot 11 of 19 from the field against Penn State and 5 of 10 from beyond the arc is the team's leading scorer at 17.1 points per game. She has posted double-figure scoring in 18 of 21 games this season.
Wisconsin has weathered a tough season playing with a thin roster. Only nine players dress since two players are sidelined with season-ending injuries and another two decided to transfer.
Meanwhile, the Lady Lions, who throttled the Badgers 84-40 at home two weeks ago for their most lopsided victory since 2001, host Purdue (18-3, 7-1) on Monday with the Big Ten standings lead on the line.
Prior to the Wisconsin loss, Penn State had won 11 consecutive games since a 67-52 loss at Connecticut on Dec. 6. Penn State's start is their fastest since starting 22-2 to open the 1993-94 season.