Two Banks of Four

In association football, the formation of a team refers to the position players take in relation to each other on a pitch. As association football is a fluid and fast-moving game, a player's position (with the exception of the goalkeeper) in a formation does not define their role as tightly as that of, for instance, a rugby player, nor are there breaks in play where the players must line up in formation (as in gridiron football). A player's position in a formation typically defines whether a player has a mostly defensive or attacking role, and whether they tend to play centrally or towards one side of the pitch.

Formations are usually described by three or more numbers in order to denote how many players are in each row of the formation, from the most defensive to the most advanced. For example, the "4–5–1" formation has four defenders, five midfielders, and a single forward. The choice of formation is normally made by a team's manager or head coach. Different formations can be used depending on whether a team wishes to play more attacking or defensive football, and a team may switch formations between or during games for tactical reasons. Teams may also use different formations for attacking and defending phases of play in the same game. Each team will have 11 players, and 11 bench players.

In the early days of football, most team members would play in attacking roles, whereas modern formations are generally split more evenly between defenders, midfielders, and forwards.

In recent decades, methods have been developed to identify team formations from tracking data, showing that formations can vary given match context.