Riley Weiss wouldn't let Columbia leave the NCAA tournament again without getting a victory.
The sophomore guard scored 14 of her 24 points in the fourth quarter, including key free throws down the stretch, to help Columbia rally from a 13-point halftime deficit and beat Washington 63-60 on Thursday night.
The historic win for the Lions came on the one-year anniversary of their first March Madness appearance, when they lost to Vanderbilt in the First Four.
"This is something that we've been working all year to do," Weiss said. "After we get this win, we'll celebrate a little bit and then get on to the next thing. We're focused on the next game."
Cecelia Collins added 12 points for the Lions (24-6), who won the First Four matchup of 11-seeds. They will face sixth-seeded West Virginia on Saturday.
Columbia, whose NCAA tournament win is just the fifth overall by an Ivy League school, trailed most of the game until the fourth quarter when Weiss got hot. Her two free throws with 18 seconds left gave the Lions a 61-57 lead. Elle Ladine hit a deep 3-pointer a few seconds later to make it a one-point game.
Weiss then swished two free throws to make it 63-60 with 12 seconds left.
Washington (19-14) had one last chance, but this time Ladine's 3-pointer was off. Perri Page grabbed the rebound and was fouled with 1.7 seconds left. She missed both free throws, but Washington had no timeouts left and a heave from 80 feet was short.
That set off a wild celebration by the Lions at midcourt.
Weiss completed a four-point play and made two other 3-pointers in the opening few minutes of the fourth quarter to give the Lions their first lead of the game.
The game was tied at 54 before Susie Rafiu hit a layup just before the shot clock expired and, after a steal by Kitty Henderson, Marija Avlijas hit a 3-pointer from the wing to make it 59-54.
Coach Megan Griffith has turned the Lions into an Ivy League power over the past few seasons. The former Columbia point guard has led the program to three consecutive regular-season conference titles, including this year's outright crown.
"I'm so grateful for just being given this opportunity to lead this program," Griffith said.
This was Washington's first NCAA appearance since 2017, when the Huskies reached the Sweet 16.
"The loss is mine, the game is on me," Washington coach Tina Langley said. "When they got some easy baskets, we were kind of stung by it."
Sayvia Sellers finished with 21 points to lead Washington. Dalayah Daniels added 17 points and 11 rebounds.
Washington hit nine of its first 12 shots to go up 19-6 early. The Lions struggled from the field, missing their first nine 3-point attempts and were down 21-10 after the first quarter. The Huskies increased the advantage to 34-21 at the half as they held Columbia to 30% shooting in the opening 20 minutes, including 2-for-15 from 3.
Information from ESPN Research and The Associated Press was used in this report.