A referee is a person who enforces the rules during a game or sporting event to keep the competition fair. When two basketball teams play, the referee watches for fouls, violations, and out-of-bounds plays, blowing a whistle and making hand signals to stop play when needed. Referees in soccer run up and down the field alongside the players, calling penalties and keeping time. In boxing or wrestling, the referee stands right in the ring to protect the athletes and ensure they follow the rules.

Being a referee requires deep knowledge of the game, quick judgment, and the ability to make unpopular decisions. Players and coaches often disagree with referees' calls, sometimes quite loudly, but a good referee stays calm and consistent. The job demands fairness: referees can't favor one team over another, even if the crowd wants them to.

As a verb, to referee means to act as the referee for a game.

Outside of sports, referee can mean anyone who settles disputes or vouches for someone's character. When applying for a job, you might list a teacher as a referee: someone who can speak honestly about your abilities and reliability.