Futsal is a variant of association football played between two teams of five players each on a court smaller than a football pitch. Its rules are based on the Laws of the Game of association football, and it also shares similarities with five-a-side football and indoor soccer.

Futsal is played between two teams of five players each, one of whom is the goalkeeper. The players mainly use their feet to propel a ball around the court with the objective of scoring goals against the opposing team by moving the ball beyond the goal line into the opposing team's goal. A futsal match consists of two periods of 20 minutes, and the team that scores more goals wins; an equal number of goals scored results in a draw. Futsal is played with a smaller and heavier ball than association football, and usually indoors on a hardcourt surface marked by lines.

The playing surface, ball and rules favour ball control and passing in small spaces. For these reasons, futsal is commonly used by coaches as a means to develop association football players. Futsal is played worldwide, but it is most popular in South America and the Iberian Peninsula, where there are many professional teams. In much of the rest of the world, the sport is primarily amateur or recreational.

Futsal comes from the Portuguese futebol de salão and from the Spanish fútbol sala or fútbol de salón, all translatable as "indoor football" (lit. 'hall football' or 'room football'). The term may have been coined by a Brazilian journalist in the 1960s. Due to a dispute between FIFA and FIFUSA (now the World Futsal Association) in the 1980s over the use of the word "football", FIFUSA started using the term futsal during its 1985 World Championship in Madrid, Spain. However, FIFA, which started organising its own international futsal tournaments in 1989, also adopted the term in the 1990s. Since then, futsal has become the officially and internationally accepted name.

Futsal started in 1930 in Montevideo, Uruguay, when a physical education teacher named Juan Carlos Ceriani ^[fr] created a version of indoor football for YMCAs.

Originally developed for basketball courts, a rule book for the sport was published in September 1933. Association football was already highly popular in the country, and after Uruguay won gold medals in the 1924 and 1928 Summer Olympics, and the 1930 FIFA World Cup, it attracted even more practitioners. Ceriani's goal was to create a team game similar to football that could be played indoors or outdoors.

While writing the rule book, Ceriani combined the principles of association football—where the ball may be touched with every part of the body except the hands and arms—with rules from other sports: from basketball, the number of players (five per team) and the game's duration (40 active minutes); from water polo, the goalkeeping rules; from hockey, the substitution rules; and from handball, the field and goal sizes.

The YMCA spread the game quickly throughout South America. Futsal was a more accessible and less physically demanding sport than association football that could be played indoors. It even helped players of other sports stay in shape year-round. These reasons convinced João Lotufo, a Brazilian, to bring the game to his country and adapt it to the needs of physical education.