A titular bishop in various churches is a bishop who is not in charge of a diocese. By definition a bishop is an "overseer" of a community of the faithful, so when a priest is ordained a bishop the tradition of the Roman Catholic and Orthodox churches is that he be ordained for a specific place. There are more bishops than there are functioning dioceses. Therefore a priest appointed not to head a diocese as its diocesan bishop, but to be an auxiliary bishop, a papal diplomat, or an official of the Roman Curia is appointed to a titular see.

A titular see in various churches is an episcopal see of a former diocese that no longer functions, sometimes called a "dead diocese". The ordinary or hierarch of such a see may be styled a "titular bishop", "titular metropolitan", or "titular archbishop".