College basketball players foul out of a game after five fouls. After a fifth foul, players are ineligible to play for the remainder of the game. That includes any overtime periods that may be played.
In college, personal fouls include common fouls, moving screens & offensive fouls, flagrant fouls, and – unlike the NBA – technical fouls.
Because the college game is shorter than the NBA, college basketball players are disqualified after a fewer number of fouls. In the NBA, players are given six fouls before disqualification.
Needless to say, college basketball games can often hinge on foul calls and player availability. That's even more true during March Madness, where defensive intensity is often cranked up higher than usual.