An Thir na tÁirdteachd

The Viscountcy of An Thir na tÁirdteachd (Rockallian: Uisiarlateachd nan Thir na tÁirdteachd, , Fernolian: Ísirliticht nan Thir na tÁirdteachd, Astrallic: Éusiorlteachd Nan Thir na tÁirdteachd or Iwsiyrtycht Nyn Îr ny tÔrdtiycht) is one of the six viscountcies of Rockall in the Seafaring Confederation. Its capital as of 1978 is Innéair Áibhan Eoighearr.

An Móir Leautheinn covers most of the south coast of Rockall to the west of the Rin na nOichte and the majority of the inland Lóda na Núille. The Meoirr also belongs to the viscountcy. It borders An Móir Leautheinn in the west, Cóste Ígheainne in the north, Líchthiach Thiair and the Rockallic Federal District in the northeast, and An Uinnia in the east, making it the only viscountcy to border all other viscountcies.