British baseball, also known colloquially in Wales as Welsh baseball, is a bat-and-ball game played in Wales, England, and to a lesser extent in Ireland and Scotland. The game emerged as a distinct sport in Merseyside, Gloucester and South Wales at the end of the 19th Century, drawing on the much older game of rounders. Teams in all locations played under the codified rules created by the National Rounders Association (later renamed as the, with the game in Wales locally organised first by the South Wales Baseball Association,, who in turn were replaced by the Welsh Baseball Union. The Irish Baseball Union were formed in 1933. Both the English Baseball Association and Welsh Baseball Union are members of the International Baseball Board.

Bat-and-ball games are field games played by two opposing teams. Action starts when the defending team throws a ball at a dedicated player of the attacking team, who tries to hit it with a bat and run between various safe areas in the field to score runs (points). The defending team can use the ball in various ways against the attacking team's players to force them off the field when they are not in safe zones, and thus prevent them from further scoring. The best known modern bat-and-ball games are cricket and baseball, with common roots in the 18th-century games played in England.