Aleague system is ahierarchy ofleagues in a sport. They are often calledpyramids, due to their tendency to split into an increasing number of regional divisions further down the system. League systems of some sort are used in many sports in many countries.

Inassociation football,rugby union,rugby league andGaelic games, league systems are usually connected by the process ofpromotion and relegation, in which teams from a lower division who finish at the top of the standings in their league are promoted (advanced to the next level of the system) while teams who finish lowest in their division are relegated (move down to a lower division). This process can be automatic each year, or can require playoffs.

In North America, league systems in the most popular sports do not use promotion or relegation. Mostprofessional sports are divided intomajor andminor leagues.Baseball and association football (known as soccer in North America) have well-defined pyramid shapes to their minor league hierarchies, each managed by a governing body (Minor League Baseball, an organization under the authority of theCommissioner of Baseball, governs baseball leagues; theUnited States Soccer Federation designates the American soccer pyramid.)Ice hockey's professional minor league system is linear, with one league at most of the four levels of the game; the ice hockey league system in North America is governed bycollective bargaining agreements and affiliation deals between theNHL,AHL andECHL.

Gridiron football does not operate on a league system. Different professional leagues play byvery different sets of rules in different seasons (theNFL plays 11-a-side on a 100-yard field in autumn and early winter, theCFL uses 12-a-side on a 110-yard field in summer and early fall, whilearena football and theminor indoor leagues each play 8-a-side on a 50-yard field in the spring and early summer). There have been attempts at forming true minor leagues for the professional game (most recently with theUnited Football League in 2024, formed as a merger between the second incarnations of theXFL andUSFL); none so far have been able to balance the major leagues' requests with the ability to maintain financial solvency.

League systems can have a negative effect on competitive balance, particularly in European professional football.^[1]

• Group tournaments
• List of professional sports leagues