The second-ranked Notre Dame Fighting Irish are Big East Tournament champions for the first time in school history.
Natalie Achonwa's layup with 1.8 seconds remaining lifted Notre Dame over the third-ranked Connecticut Huskies, 61-59.
The Fighting Irish appeared in the Big East title game for the seventh time, having lost to Connecticut in each of their six prior finals appearances.
Kayla McBride had 23 points for Notre Dame (31-1), which got 16 points from Jewell Loyd. Skylar Diggins, who got the assist on the game-winning basket, tallied 12 points, six assists and five steals.
Earlier Tuesday, Notre Dame announced it would be joining the ACC starting next season -- a year earlier than expected.
Stefanie Dolson ended with 18 points and 14 rebounds for the Huskies (29-4), who had captured the previous five tournament titles.
Connecticut scored six straight points late in the contest to tie the game at 59.
However, Diggins stole an errant pass from Kaleena Mosqueda-Lewis with time winding down, and after making her way through a few defenders, found Achonwa wide open under the basket for the game-winner.
Kelly Faris' 3-point heave was off the mark and the Irish celebrated their 26th straight victory.