Seven-ball is a pool game with rules similar to nine-ball, though it differs in two key ways: the game uses only seven as implied by its name, and play is restricted to particular pockets of the table. William D. Clayton is credited with the game's invention in the early 1980s.
At the start of the game, balls one through seven are in a hexagonal configuration, with the 1-ball placed at the rack's , centered over the table's , the 7-ball placed at the rack's center, and all other balls placed clockwise (see photo top right). Immediately following the , the opponent must elect three pockets along one of the table's , and the player who broke is automatically assigned the three pockets situated along the opposite long rail. Once that selection is made, balls 1–6 may be in any pocket in rotation, starting with the one, as the object ball. Balls pocketed via combinations off of the object ball are legal. The 7-ball must be pocketed in the called side to be a legal win. Scratches on any object ball allow the opponent ball-in-hand, but the sunk ball remains potted. Scratching on the 7-ball is a loss. Pocketing the 7-ball in any other pocket than the called side is a loss.
A special 7-ball was designed for television matches by Charles Ursitti (billiards historian, referee and Willie Mosconi's one time manager) to address the problem that the color of the seven and three balls in a standard set of pool balls are nearly indistinguishable when viewed on a TV screen. The ball adopts the of the with the color of the black , the "" of their respective namesake games.
The original informal incarnation of seven ball led to a variant professional ruleset that enjoyed a brief heyday in the Sudden Death Seven-ball series of pro tournaments, broadcast on the American cable TV network ESPN from 2000 to 2005.