For the Dilated Peoples album, see Expansion Team (album)

An expansion team is a term used for a brand new team in a sports league. The term is most commonly used in reference to the North American major professional sports leagues, but is applied to sports leagues worldwide that use a closed franchise system of league membership. The term comes from the fact that the league expands its presence into new cities.

In North America, expansion takes place in response to population growth and geographic shifts of population, driven by the resulting financial opportunity made possible by such demographic change. For example, Major League Baseball was limited to 16 teams located north and east of St. Louis, Missouri for the first half of the 20th century. During this time, the United States population doubled and expanded to the south and west. Rival interests explored the possibility of forming a rival league in these untapped markets. To forestall this possibility, one of the measures MLB took was to expand by four teams in 1961 and 1962. Over the past four decades, MLB expanded further to its current membership.

When an expansion team begins play, they are generally stocked with less talented free agents and inexperienced staffs. Additionally, prospective owners must pay extremely steep fees to the league as well as expensive start-up costs such as stadiums and facilities. As a result, most expansion teams are known for their poor play during their inaugural season. However, with increasing parity (mainly due to first pick drafts) and experience, some are known to win championships only a few years after their first season.

Most teams are considered as an expansion team usually in their first season and sometimes in their second season. A team that moves to another location and/or changes its name is generally not considered an expansion team. They are known as relocated teams. If the name changed they are known as renamed teams. The two major exceptions to this rule are the Baltimore Ravens in the NFL and Houston Dynamo in the MLS.

Cities and/or regions with large populations that lack a team are generally regarded to be the best candidates for new teams. For example, the National Football League (NFL) has recently considered Los Angeles, CA to be the best possibility for a brand new NFL team.