An
auxiliary bishop, in the
Roman Catholic Church, is an additional
bishop assigned to a
diocese because the diocesan bishop is unable to perform his functions, the diocese is so extensive that it requires more than one bishop to administer, or the diocese is attached to a royal or imperial office needing the diocesan bishop's protracted location at court. According to
canon law, no bishop can be
ordained without title to a certain and distinct
episcopal see which he governs either actually or potentially, therefore auxiliary bishops are
titular bishops to
sees that no longer exist.