Blackball (sometimes written black ball or black-ball) is a pool (pocket billiards) game that is popular in the United Kingdom, Ireland, France, Spain, Malta, South Africa, Australia, and some other countries. In the UK and Ireland it is usually called simply "pool". The game is played with sixteen balls (a cue ball and fifteen usually unnumbered object balls) on a small (6 ft x 3 ft or 7 ft x 4 ft) pool table with six pockets.
Blackball is an internationally standardised variation of the popular bar and club game eightball pool (a.k.a. eight-ball pool or 8-ball pool), closely related to the originally American and now professionally internationalised game eight-ball. The two main sets of playing rules are those of the World Pool-Billiard Association (WPA, the International Olympic Committee-recognised governing body of pool) and its affiliate the European Blackball Association (EBA), known as "blackball rules", and the older code of the World Eightball Pool Federation (WEPF), often referred to as "world rules" or the "eightball pool rules".
Eightball pool (and thus its standardised form, blackball), like international-style eight-ball, is derived from an earlier game invented around 1900 and first popularised in 1925 under the name B.B.C. Co. Pool by the Brunswick-Balke-Collender Company. Like blackball and eightball pool today, this forerunner game was played with seven yellow and seven red balls, unnumbered (in contrast to the international-style numbered stripes and solids, sometimes called American-style or kelly pool balls in Commonwealth English), a black ball (numbered "8" or unnumbered), and the white cue ball. The game had relatively simple rules compared to the modern game.