- The League of Nations was an intergovernmental organisation founded on 10 January 1920 as a result of the Treaty of Versailles that ended the First World War. The league was the first international organisation whose principal mission was to maintain world peace.
- The American League is one of the two major professional baseball leagues in the United States and Canada, along with the National League. The American League was formed in 1901 as a rival circuit to the National League.
- The Ivy League is an athletic conference composed of eight private research universities in the Northeastern United States. The conference was founded in 1954 as the Intercollegiate Conference of Faculty Representatives (IC4).
- The League of Women Voters of the United States is a nonpartisan political organisation that encourages informed and active participation in government. It was founded in 1920 and is headquartered in Washington, D.C.
These are just a few examples of leagues, which can be found in many different fields and areas of interest.