Castleblayney or Castleblaney (Irish: Baile na Lorgan, formerly Caisleán Mathghamhna) is a town in County Monaghan, Ireland. The town has a population of 3,634 according to the 2011 census.Castleblayney lies near the border with County Armagh (Northern Ireland) and is on the N2 road from Dublin to Derry. Its name is often shortened to "Blayney" or "Blaney" by locals.