Harry Diamond (1908–1996) was a socialist and an Irish nationalist. He was the MP for Belfast Falls in the Parliament of Northern Ireland, and later the leader of the Republican Labour Party.
In 1927, Diamond was the main initiator and first chairman of O'Donnell's GAA. He later became chairman of Antrim GAA.
Diamond was an active nationalist before the Second World War and in 1933 was sentenced to a month in jail for refusing to pay a fine given out for addressing an illegal rally in support of republican prisoners. The following year, he stood in the Belfast Central by-election as an "Anti-Partition" candidate.
Diamond was first elected in the 1940s at a time when the Irish Labour Party was in government in the Republic of Ireland. He left the Labour Party because of the (indirect) consequences of that government's travails over the Mother and Child Scheme and the demand of the majority of Irish Labour members in Belfast that the party should challenge the entrenched power of the Catholic Church in Ireland. Diamond opposed these demands and left the party to fight a city council by-election against a Protestant Irish Labour Party supporter of reform. Diamond lost the by-election but viciously attacked the Labour Party for being in the grip of Communism, thereby effectively destroying it as a political force.