The Archdiocese of Cardiff-Menevia (Latin: Archidioecesis Cardiffensis-Menevensis; Welsh: Archesgobaeth Caerdydd-Mynyw) is a Latin archdiocese of the Catholic Church which covers south Wales and the county of Herefordshire in England. The Metropolitan Province of Cardiff covers all of Wales and parts of England. Cardiff's one suffragan diocese is the Diocese of Wrexham.

The origin of the modern diocese can be traced to 1840 when the Apostolic Vicariate of the Welsh District was created out of the Western District of England and Wales. The Welsh District consisted of the whole of Wales and the English county of Herefordshire. When Pope Pius IX judged that the time was right to re-establish the Catholic hierarchy in Wales and England in 1850, the southern half of the Welsh District became the Diocese of Newport and Menevia and was a suffragan of the Archdiocese of Birmingham. It had its pro-cathedral at Belmont Abbey. In 1895, boundaries were redrawn, and the territory covering Glamorgan, Monmouthshire and Herefordshire was named the Diocese of Newport. Finally, in 1916, without further adjustment of boundaries, the territory was raised to the status of an archdiocese, and given the title Archdiocese of Cardiff. The episcopal seat is St David's Cathedral.

As all of the Roman Catholic dioceses in Wales are part of the ecclesiastical province of Cardiff the history of the archdiocese and its suffragan dioceses are intertwined:

• 29 September 1850: Universalis Ecclesiae: The Roman Catholic Church in Wales is split between the Diocese of Shrewsbury in the north and the Diocese of Newport and Menevia in the south.
• 1852: Francis Richard Wegg-Prosser, a landowner in Hereford, converts to Catholicism.
• 15 February 1854: Wegg-Prosser sets about building a church and the foundation stone is laid on his Belmont estate.
• 1857: Construction of the Belmont monastic buildings starts.
• 21 November 1859: Most of it is built and it becomes a Benedictine priory. The abbey continues to be enlarged (chancel extended in 1865).
• 4 September 1860: The cathedral priory is consecrated.
• 4 July 1895: The Diocese of Newport and Menevia splits. Glamorgan, Monmouthshire and Herefordshire become the Diocese of Newport. The rest of Wales, including North Wales from the Diocese of Shrewsbury, becomes the Apostolic Vicariate of Wales.
• 12 May 1898: The Apostolic Vicariate of Wales becomes the Diocese of Menevia with its pro-cathedral in Wrexham.
• 7 February 1916: The Diocese of Newport becomes the Archdiocese of Cardiff and it is decided that St David's Church in Cardiff would become the cathedral.
• 12 March 1920: St David's Cathedral, Cardiff, is officially made the metropolitan cathedral.
• 12 February 1987: The Diocese of Menevia is split. The north becomes the Diocese of Wrexham with its cathedral remaining in Wrexham. The south remains the Diocese of Menevia and sets up Swansea Cathedral.
• 12 September 2024: Pope Francis creates the Archdiocese of Cardiff-Menevia by merging the Archdiocese of Cardiff and the Diocese of Menevia.

The current ecclesiastical territory of the archdiocese comprises the Welsh principal areas of Blaenau Gwent, Bridgend, Caerphilly, Cardiff, Carmarthenshire, Ceredigion, Merthyr Tydfil, Monmouthshire, Neath Port Talbot, Newport, Pembrokeshire, Rhondda Cynon Taf, Swansea, Torfaen, the Vale of Glamorgan and the part of Powys comprising the historic counties of Brecknockshire and Radnorshire, with the English county of Herefordshire. Altogether there are 61 parishes.

• Thomas Joseph Brown, O.S.B. (Appointed on 5 June 1840 – Became Bishop of Newport and Menevia on 29 September 1850)

• Thomas Joseph Brown, O.S.B. (Appointed on 29 September 1850 – Died on 12 April 1880)
• John Cuthbert Hedley, O.S.B. (Appointed on 18 February 1881 – from 1895, Bishop of Newport only – Died on 11 November 1915)

• James Romanus Bilsborrow, O.S.B. (Appointed on 7 February 1916 – Resigned on 16 December 1920)
• Francis Edward Joseph Mostyn (Appointed on 7 March 1921 – Died on 25 October 1939)
• Michael Joseph McGrath (Appointed on 20 June 1940 – Died on 28 February 1961)
• John Aloysius Murphy (Appointed on 22 August 1961 – Retired on 25 March 1983)
• John Aloysius Ward, O.F.M. Cap. (Appointed on 25 March 1983 – Resigned on 26 October 2001)
• Peter David Smith (Appointed on 26 October 2001 – Translated to Southwark on 30 April 2010)
• George Stack (Appointed on 19 April 2011. Installed on 20 June 2011 – 20 June 2022)
• Mark O'Toole (Appointed on 27 April 2022. Installed on 20 June 2022 – 12 September 2024)

• Mark O'Toole (12 September 2024 – present)

• John Edward Cuthbert Hedley, O.S.B. (1873–1881), appointed Bishop here
• Daniel Joseph Mullins (1970–1987), appointed Bishop of Menevia

• Peter Collins (bishop), appointed Bishop of East Anglia in 2022
• Daniel Joseph Hannon, appointed Bishop of Menevia in 1941
• David James Mathew, appointed auxiliary bishop of Westminster in 1938
• Edwin Regan, appointed Bishop of Wrexham in 1994
• Francis John Vaughan, appointed Bishop of Menevia in 1926

There are a total of six deaneries in the Archdiocese of Cardiff, each of which cover several churches in that area, overseen by a dean.

The deaneries include:

• Bridgend Deanery
• Cardiff Deanery
• Hereford Deanery
• Newport Deanery
• North Gwent Deanery
• Pontypridd Deanery

• Archdiocese of Cardiff website
• Cardiff Metropolitan Cathedral
• Wales and the Marches Catholic History Society Archived 10 November 2011 at the Wayback Machine
• Cardiff Catholic Archives
• GCatholic.org
• Catholic Hierarchy