After the Church in England broke communion with the Catholic Church, by decree of the Irish Parliament, the Church of Ireland became the Established Church in the Kingdom of Ireland. The English-speaking minority mostly adhered to the Church of Ireland or to Presbyterianism, while the Roman Catholic Church undertook extensive mission work and retained the allegiance of the majority of the population in Ireland as a whole. From the 1830s onwards, many Anglican dioceses were merged, in view of declining membership. The sees of Derry and Raphoe were united in 1834.^[1] It is for this reason that the united diocese has two cathedrals.

• The Cathedral Church of St Columb, Derry, Northern Ireland.
• The Cathedral Church of St Eunan, Raphoe, County Donegal, Republic of Ireland.

The following is a basic list the bishops.^[1]

• List of Anglican dioceses in the United Kingdom and Ireland
• Roman Catholic Diocese of Derry
• Roman Catholic Diocese of Raphoe
• Plantation of Ulster

• Diocesan homepage