In sports, an ejection is the removal of a participant from a contest due to a violation of the sport's rules. The exact violations that lead to an ejection vary depending upon the sport, but common causes for ejection include unsportsmanlike conduct, violent acts against another participant that are beyond the sport's generally accepted standards for such acts, abuse against officials, violations of the sport's rules that the contest official deems to be egregious, or the use of an illegal substance to better a player's game. Most sports have provisions that allow players to be ejected, and many allow for the ejection of coaches, managers, or other non-playing personnel. In sports that use penalty cards, a red card is often used to signal dismissals. In some sports, another player is permitted to enter the game in place of the player who has been ejected, but in others the team is required to continue the game with a reduced number of players.

Unsportsmanlike conduct is a foul or offense in many sports that violates the sport's generally accepted rules of sportsmanship and participant conduct. Examples include verbal abuse, taunting of an opponent or a game official, an excessive celebration following a significant play, or feigning injury. The official rules of many sports include a general provision whereby participants or an entire team may be penalized or otherwise sanctioned for unsportsmanlike conduct.