Second International (1889–1916), founded after the expulsion of Anarchists from the First International, and a direct ancestor of the Socialist International
Third International (1919–1943), known as the Communist International or Comintern, founded by Vladimir Lenin
Fourth International (1938-), founded by Leon Trotsky in opposition to the corruption of the Comintern by Stalinism
Socialist International (1951-), founded as the Labour and Socialist International (1919–1940), and refounded as the Socialist International in 1951
Fifth International, a widely mooted but never established successor to the previous Internationals
Liberal International, the political international federation for liberal political parties