Republican Sinn Féin or RSF () is an Irish republican political party in Ireland. RSF claims to be heirs of the Sinn Féin party founded in 1905 and took its present form in 1986 following a split in Sinn Féin. RSF members take seats when elected to local government in the Republic of Ireland, but do not recognise the validity of the Partition of Ireland. It subsequently does not recognise the legitimacy of the parliaments of Northern Ireland (Stormont) or the Republic of Ireland (Leinster House), so the party does not register itself with them.