The Socialist Labour Party was a political party in Ireland in the mid 1970s to early 1980s formed under the leadership of the late Matt Merrigan (General Secretary, A.T.G.W.U.) and Noel Browne (TD). The SLP tried unsuccessfully to build the 'Left Alternative', a coalition of progressive organisations and individuals, aimed at addressing what they saw as the cultural and economic impoverishment of Irish society by the establishment parties of Fianna Fáil, and Fine Gael.

The SLP regarded itself as highly progressive. It allowed for the right of factions to organise within the Party. However, the various Trotskyist groups, within, became so pre-occupied with this provision that they effectively abandoned the uniting principal, the raison d'etre of the Party.

In the absence of Party unity, the Executive Committee took the decision to dissolve the SLP. The SLP won much admiration for its principled and progressive stance within the Irish Left.

Only in recent years have the various factions, parties and movements of the Left in Ireland begun to learn from the experience of the SLP and realise the original goals and visions of Matt Merrigan and Noel Browne.