 It covers a rural area on the border between Northern Ireland and the Republic of Ireland including much of south west Ulster, taking in most of counties Fermanagh and Monaghan and parts of counties Cavan, Leitrim and Donegal.The diocese has two diocesan cathedrals, St Macartan's Cathedral, Clogher and St Macartin's Cathedral, Enniskillen, yet having a single Dean and Chapter between them.The Diocese was formed in 1111 at the Synod of Rathbreasail as the see for the Kingdom of Uí Chremthainn.