A common videogame concept. A Harder-than-average enemy or group of enemies placed at the end of a level or group of levels that you must fight. Often, the Boss will have some kind of unique attack or defense that you must be wary of, and some kind of unique weakness you must exploit.

This concept is not native to a single game genre. Mario has Boss Battles. Mega Man has Boss Battles. Zelda has Boss Battles. Final Fantasy, Phantasy Star, Lunar... all of them have Bosses, none of the Bosses are pacifist. Hence, they all have Boss Battles.