Indoor soccer or arena soccer, or six-a-side football in the United Kingdom, is a game derived from association football adapted for play in an indoor arena such as a turf-covered hockey arena or skating rink. The most important difference in play is that the indoor field is surrounded by a wall instead of touch lines, resembling more of a hockey rink than a soccer pitch. The ball can be played directly off the wall, which eliminates many frequent stoppages that would normally result for throw-ins, goal kicks and corner kicks, and generally results in a faster paced game. The term "indoor soccer" is so well known as a description of the different style of the game that it is even used to describe similar fields which are built outdoors.

Indoor soccer is one of several distinct variants of the game of association football designed for play in indoor arenas. Indoor soccer is most popular in the United States, Canada and Mexico, with several amateur, collegiate and professional leagues functioning. It is also popular in Brazil, where it is called showbol. Other variants of indoor football, such as futsal and five-a-side football, are more popular outside North America. These variants have different rules and governing bodies from those of indoor soccer.