[1] The Diocese of Menevia covered an area of 9,716 km2 (3,751 sq mi) roughly consisting of Carmarthenshire, Ceredigion, Neath Port Talbot, Pembrokeshire, the City and County of Swansea and the ancient counties of Brecknockshire and Radnorshire.
[1] The see was in Swansea, where the seat was located at Saint Joseph's Cathedral.
The present territory of the Diocese dates from the restructuring of the Province of Cardiff by Pope John Paul II on 12 February 1987.
The Diocese was overseen by the Apostolic Administrator The Most Reverend Archbishop George Stack of the Archdiocese of Cardiff.
Following Stack's retirement in 2022, Pope Francis appointed Bishop Mark O’Toole as metropolitan archbishop of Cardiff and bishop of Menevia, Wales, uniting the two sees in persona Episcopi.