Nine-ball is a contemporary pocket billiards (pool) game, with historical beginnings rooted in the United States and traceable to the 1920s. The game may be played in social and recreational settings by any number of players (generally one-on-one) and subject to whatever rules are agreed upon beforehand, or in league and tournament settings in which the number of players and the rules are set by the sponsors. During much of its history, nine-ball has been known as a "money game" in both professional and recreational settings; but today, in major tournament settings, it is respected and remains the dominant game (although ten-ball is gaining momentum).
In recent years, nine-ball has become the game of choice in Championship Tournament matches in the United States, basically because a series of games (the "match") proceeds quickly, lends itself well to the time constraints of television coverage, and tends to keep the audience engaged. The sports network ESPN has been, for several years, a major catalyst for the popularity of nine-ball and a major sponsor of championship play.