Squash is an indoor racquet sport played by two players, in a four-walled court with a small, hollow rubber ball.

Squash historians believe that the game originated in the 19th century at the Harrow School, just outside London, as a derivative of the game of Racquets. The first recorded construction of purpose-built squash courts was at Harrow in the 1860s. It is possible that earlier squash courts were created at Harrow by sub-dividing a racquets court, which is almost exactly the size of three Squash courts (to allow more players on the courts at the same time).

Squash provides an excellent cardio-vascular workout. In one hour of squash, a player may expend 700 to 1000 calories (3,000 to 4,000 kJ) which is significantly more than most other sports. The sport also provides a good upper and lower body workout by utilising both the legs to run around the court and the arms/torso to swing the racquet.

Rallies between experienced players may involve 30 or more shots and therefore there is a very high premium on fitness, both aerobic and anaerobic. As players become more skilled and, in particular, better able to retrieve shots, points often become a war of attrition. At the top levels of the game, the fittest player will invariably win the match.