- See Workers Power (Ireland) for the Irish Workers' Group which was a member of the League for a Fifth International.
The Irish Workers' Group (IWG) was a Marxist political party in Ireland. It originated as the Irish Workers Union, which later called itself the Irish Communist Group, and contained a variety of people who all considered themselves to be Marxists. Some were from an Irish Republican background, and some, including Gerald Lawless, also known as Gerry Lawless, became involved in Saor Éire. 
In time the group developed distinct Trotskyist and Maoist wings. The latter broke away to form the Irish Communist Organisation, which evolved into the British and Irish Communist Organisation. The former became the Irish Workers' Group,and produced a paper Irish Militant and a theoretical journal An Solas/Workers' Republic.
By 1967 the IWG, then based in London among exiled political activists, was failing and handed over their journal to Sean Matgamna and Rachel Lever who were about to launch Workers Fight. A section with support in Ireland then formed the League for a Workers Republic which entered discussions with the Socialist Labour League, British affiliate of the International Committee of the Fourth International.  
Other members of the IWG later influential in the Irish far-left were Eamonn McCann, a leader of the Socialist Workers Party, and Michael Farrell, a leader of the now defunct People's Democracy. This group seems to have ceased to exist in the late 1960s.
A later Irish Workers' Group was an organisation that split from the Socialist Workers Movement in 1976. It maintained links with the British Workers Power group and the League for a Fifth International. 
- See International Trotskyism, 1929-1985 by Robert Jackson Alexander, Duke University Press, 1991 (pg. 570).
- Sunday Independent, "Extreme Communists plan branch in Dublin", May 9th, 1965 (pgs. 1,6).This article describes the ICG as a London-based Maoist group and states that Gerald Lawless, Angela Clifford, Brendan Clifford, Michael Murphy, Tom O'Leary, Bernard P. Canavan and Liam Eamon Daltun are ICG members.
- Encyclopedia of British and Irish Political Organizations by Peter Barberis, John McHugh, Mike Tyldesley. Continuum 2005 (pg. 232).
- Glossary of the Left in Ireland 1960-83