The Socialist International
- Worldwide organization of major social democratic and labour parties. Site includes background, membership, resolutions, meeting reports, regular newsletter.
- http://www.socialistinternational.org/

International Socialist Tendency
- Socialist groups in various countries which follow the leadership of the Socialist Workers Party in Britain.
- http://www.istendency.net/

The World Socialist Movement
- Comprehensive site offers analysis of historical, encomomic and current political events. WSM's idea of socialism accepts Marxism but rejects Leninism, Trotskysim and reformism. WSM has "companion parties" in several countries.
- http://www.worldsocialism.org/

International Communist Union
- The ICU is the international tendency led by the French Marxist group Union Communiste which is better known by the name of its publication Lutte Ouvriere. LO has been around since the 1930s but split with Trotsky by opposing the creation of the Fourth In
- http://www.union-communiste.org/

International Communist League
- Publishers of Workers' Vanguard and The Spartacist, the ICL is organised as the Spartacist League in several countries and the Trotskyist League/Lige Trotskyiste in Canada and France. The original group split from the (US) Socialist Workers Party in the 1
- http://www.icl-fi.org/

International Committee of the Fourth International
- Led by David North of the (US) Socialist Equality Party, the ICFI is a small remnant of the original ICFI formed in the 1950s. Various groups such as the Lambertists (ISFI), the Spartacists, the Healyites and various others have split from it. Site contai
- http://www.wsws.org/sections/category/icfi/icfi.shtml

International Bureau for the Revolutionary Party
- An anti-Stalinist but non-Trotskyist international formation centred in Italy and with a British section, the Communist Workers' Organisation. The IBRP is descended from Bourdigaist tradition which was expelled from the Third International in the 1920s.
- http://www.ibrp.org/

International Bolshevik Tendency
- The IBT's journal is 1917, providing a bolshevik analysis of current and historical events of interest to the worker's movement. The IBT split from the Spartacist League/International Communist League in the late 1970s/early 1980s.
- http://www.bolshevik.org

The Fourth International (United Secretariat)
- Worldwide marxist organization.Key leaders have included Leon Trotsky, Ernest Mandel, Pierre Frank and Livio Maitan.
- http://www.isg-fi.org.uk/fi/fi1.htm

Committee for a Workers' International - CWI
- International democratic Marxist tendency operating in over 35 countries worldwide. Founded by the former Militant Tendency in Britain (now the Socialist Party) in 1974.
- http://www.socialistworld.net