Yes a number 16 seed has beat a number one seed in the NCAA Basketball tournament, but it was in the womens' tournament. In 1988, 16th seed Harvard beat 1st seed Stanford in the womens' tourney. (Answer by Mymomisnfat)
It also happened in 2018 when the University of Maryland - Baltimore County (16th seed in the South) beat the University of Virginia (1st seed in the South) by a score of 74 - 54.
A 4 seed.
Since the NCAA implemented the 64 seed tournament format in 1985, the lowest seed to make it to the NCAA championship game was #8 seeded Villanova in 1985.
16th
1 in 16
UNLV was a #1 seed when they won the NCAA Men's Basketball Championship in 1990.
Duke was the only number one seed to advance.
There has been two number eight seeds (the lowest seeds) to make it to the title game: * UCLA in 1980 and *Villanova in 1985 Villanova won the national championship that year
2011 NCAA Final Four, #8 seed Butler, facing #11 seed Virginia Commonwealth. 1985 NCAA Final Four, #8 seed Villanova, defeated #1 Georgetown to win the National Championship. 1980 NCAA Final Four, #8 seed UCLA, lost to #2 Louisville in the National Championship game.
Marquette was the #16 seed in the NCAA Men's basketball tournament in 1977. They advanced and won the championship. They were also the only team to ever beat all 4 #1 seeds during the ncaa tournament.
The Butler's seed in the 2010 NCAA Men's Basketball Tournament was number 5 in the West region. They went on an incredible run to the national championship game as a mid-major school, eventually falling to Duke in a close game.
Since seeding was added as a component of the NCAA men's basketball tournament in 1979, the lowest-seeded team to win the championship was Villanova, whichwas a #8 seed in 1985.
5