The Socialist International (SI) is a political international or worldwide organisation of political parties which seek to establish democratic socialism. It consists mostly of social-democratic, socialist and labour political parties and organisations.
Although formed in 1951 as a successor to the Labour and Socialist International, it has antecedents in the late 19th century. The organisation currently includes 132 member parties and organisations from over 100 countries. Its members have governed in many countries, including most of Europe. In 2013, a schism in the SI led to the establishment of the Progressive Alliance.
The current secretary general of the SI is Benedicta Lasi (Ghana) and the current president of the SI is the prime minister of Spain, Pedro Sánchez, both of whom were elected at the last SI Congress held in Madrid, Spain, in November 2022.
The International Workingmen's Association, also known as the First International, was the first international body to bring together organisations representing the working class. It was formed in London on 28 September 1864 by socialist, communist and anarchist political groups and trade unions. Tensions between moderates and revolutionaries led to its dissolution in 1876 in Philadelphia.
The Second International was formed in Paris on 14 July 1889 as an association of the socialist parties. Differences over World War I led to the Second International being dissolved in 1916.
The International Socialist Commission (ISC), also known as the Berne International, was formed in February 1919 at a meeting in Bern by parties that wanted to resurrect the Second International. In March 1919, Communist parties formed the Communist International ("Comintern"), the Third International, at a meeting in Moscow.
Some parties did not want to be a part of the resurrected Second International (ISC) or Comintern. They formed the International Working Union of Socialist Parties (IWUSP, also known as Vienna International, Vienna Union, or Two-and-a-Half International) on 27 February 1921 at a conference in Vienna.