A type of defensive scheme in virtually any sport that involves one team's players attempting to prevent the other team's players from receiving the ball (or puck, or whatever object is passed back and forth in the particular sport). In a man to man defense, each defender picks an individual player on the other team to guard and to prevent from receiving the ball, and stays with that player whereever he or she may roam on the playing surface while the attacking team has possession.

Contrast this to zone defense.