The seventh-seeded Wolverines (26-11) have won seven straight — six since a frightening plane accident before the Big Ten Tournament. They also earned a ticket to the Midwest Regional in Kansas City, Missouri, their first since 2014.
Donovan Mitchell scored 19 points and Deng Adel had 16 points to lead Louisville (25-9), which had made the Sweet 16 in its last four NCAA Tournament appearances.
But Wagner bailed out the Wolverines from a poor game.
Trailing 45-36 with 16:09 to play, the German native scored on a layup to start a 17-6 run that gave Michigan its first lead since the opening minutes. And after Wagner's 3-pointer broke a 55-55 tie with 6:39 to go, the Wolverines led the rest of the way.