Virginia entered the NCAA Tournament as the No. 1 overall seed after going 31-2 this season, including 20-1 in ACC competition.
But the Cavaliers couldn't get anything generated on offense and the nation's top-ranked defense couldn't contain American East Conference champions.
The 74 points were the most Virginia had allowed this year.
Lyles was the catalyst.
He diced up Virginia's defense in the second half, getting the hole easily on six different occasions and making easy layups. He also knocked down a pair of 3-pointers as UMBC built a 16-point lead.
PUT SOME RESPECK ON IT! WE HAVE DEFEATED NO.1 OVERALL SEED VIRGINIA 74-54— UMBC Athletics (@UMBCAthletics) March 17, 2018
Lyles finished with 23 of his points in the second half and Joe Sherburne finished with 14 points.
The game was tied at halftime, but the Retrievers came out confident and motivated in the second half and built a double-digit lead that Virginia could never erase.
Sherburne scored on an and-one drive and then knocked down a 3-pointer from the top of the key after a behind-the-back pass from KJ Maura. After Virginia made a foul shot, the shifty 5-foot-8, 140-pound Maura drove the lane for uncontested layup.
A Tony Bennett timeout couldn't stop the bleeding, as Lyles hit two more 3's and Sherburne hit one to extend UMBC's lead to 14 with 14:57 left in the game. Lyles was fouled on a 3-point shot and suddenly the Retrievers led by 16.
A corner 3-pointer and a layups off a fastbreak by Arkel Lamer gave UMBC its biggest lead at 67-48. From there, the party was on as chants of "UMBC" rang through the arena.
It was yet another early exit for the Cavaliers in a season that seemed to hold so much promise.
UMBC: Despite being undersized and unknown, they shocked the world and made history with an epic game.
Virginia: This isn't the first time Virginia has struggled as the No. 1 seed. The Cavaliers trailed by five at halftime in 2014 to Coastal Carolina but went on to win 70-59.
UMBC: Will face No. 9 seed Kansas State on Sunday in the second round.