Born Nov. 12, 1917, in Cork. Leader in the Irish workers’ movement. Bus conductor.
O’Riordan was a member of an international brigade in the National Revolutionary War in Spain (1936–39). In 1948 he was a cofounder of the Irish Workers’ League, which after 1962 was called the Irish Workers’ Party (IWP). He became secretary of the Executive Committee of the league in 1951 and later became permanent secretary of the Executive Committee of the IWP. After the creation of a united Communist Party of Ireland (CPI) as a result of the merger in 1970 of the IWP and the Communist Party of Northern Ireland, he became secretary of the Executive Committee of the CPI. Since October 1971 O’Riordan has been general secretary of the CPI.