What is the probability that a 6 seed wins the NCAA championship game?
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.