Racquetball is a racquet sport played with a hollow rubber ball in an indoor or outdoor court. Joe Sobek is credited with inventing racquetball in 1950, adding a stringed racquet to the game to increase velocity and control. Unlike most racquet sports, such as tennis or badminton, the court's walls, floor, and ceiling are legal playing surfaces (sometimes, depending on the rules), rather than out-of-bounds.

Racquetball games can be played with two, three or four players, with two player or singles matches being most common. Two player games are called singles or "one-up" (1 vs. 1 for the entire game), while four player games are doubles with two pairs playing against each other (2 vs. 2 for the entire game). Tournament competitions have divisions for singles or doubles or both.

Three-player games are mostly commonly called "Cut-throat" and sometimes "Ironman" (2-on-1 for the entire game) where each player takes turns serving to the other two, who play as a team against the serving player. Another 3 player game is "California," or "In-and-Out" where play is 1 vs. 1 with the third player remain in the back court, out of play, while the other two play a rally; the rally winner then serves to the player who was sitting out, and the rally loser stays out of play. Another 3 player variation is "Sevens" in which one player plays against two players as a team, with the game being played to 7 points; if the two player team gets to 7 first, the game is over, but if the solo player gets to 7 first then the game continues to 14; if the solo player again reaches 14 first, then the game continues to 21, where the game ends regardless of whether the solo player or the two player team reach 21 first. (more)