A pro-cathedral is a parish church that is temporarily serving as the cathedral or co-cathedral of a diocese, or has the same function in a Catholic missionary jurisdiction that is not yet entitled to a proper cathedral, such as an apostolic prefecture or apostolic administration.
In Ireland, the term is used to specifically refer to St. Mary's Pro-Cathedral in Dublin, the seat of the Roman Catholic Archbishop of Dublin since the Reformation, when Christ Church Cathedral and St. Patrick's Cathedral was occupied by the Church of Ireland.
In Scotland, the term is used to refer to St. Mary’s Pro-Cathedral in Edinburgh, the seat of the Archbishop of Saint Andrews and Edinburgh, as the original St. Andrews Cathedral was abandoned after the Scottish Reformation in 1560 and is currently in a ruinous state. St. Andrew's Pro-Cathedral in Glasgow has been the seat of the Roman Catholic Archbishop of Glasgow since 1889. The original Glasgow Cathedral however had been re-established as the Church of Scotland’s High Kirk of Glasgow after the Scottish Reformation.