A co-cathedral is a cathedral church which shares the honor of being a bishop's seat, or cathedra, with another cathedral. Instances of this occurred in England before the Protestant Reformation in the dioceses of Bath and Wells, and of Coventry and Lichfield, hence the names of these dioceses. In Ireland, an example occurs at Dublin, where Christchurch and St. Patrick's are jointly the cathedral churches of that diocese. In France the bishop of Couserans (a see suppressed at the Revolution) had two co-cathedral churches at St Lizier , and the bishop of Sisteron (a see also suppressed) had a second throne in the church of Forcalquier which is still called La Con-cathédrale.

In the United States, the Roman Catholic diocese that encompasses most of the state of West Virginia is known as the Diocese of Wheeling-Charleston after its two cathedral cities. The Archdiocese of Saint Paul and Minneapolis in Minnesota has the Cathedral of Saint Paul and the Basilica of Saint Mary as its co-cathedrals. Other instances include the Diocese of Galveston-Houston in Texas and the Diocese of Pensacola-Tallahassee in Florida. Each of these dioceses has a co-cathedral in each of its see cities. In the Episcopal Church, both the Diocese of Iowa and the Diocese of Minnesota have two cathedrals in different cities; however, they are not styled "co-cathedrals".

In the case of York the collegiate churches of Beverley, Ripon and Southwell were almost in the same position, but although the archbishop had a stall in each he had no diocesan cathedra in them, and the chapters were not united with that of the metropolitan church in the direct government of the diocese, or the election of the archbishop, nor had they those other rights which were held to denote the cathedral character of a church.