The Second International (1889–1916) was an organisation of socialist and labour parties, formed on 14 July 1889 at two simultaneous Paris meetings in which delegations from twenty countries participated. The Second International continued the work of the dissolved First International, though excluding the powerful anarcho-syndicalist movement. While the international had initially declared its opposition to all warfare between European powers, most of the major European parties ultimately chose to support their respective states in World War I. After splitting into pro-Allied, pro-Central Powers, and antimilitarist factions, the international ceased to function. After the war, the remaining factions of the international went on to found the Labour and Socialist International, the International Working Union of Socialist Parties, and the Communist International.

The Socialist League was an early revolutionary socialist organisation in the United Kingdom. The organisation began as a dissident offshoot of the Social Democratic Federation of Henry Hyndman at the end of 1884. Never an ideologically harmonious group, by the 1890s the group had turned from socialism to anarchism, and disbanded in 1901.