The Roman Catholic Diocese of Eisenstadt (Latin: Dioecesis Sideropolitanus) is a diocese located in the city of Eisenstadt in the Ecclesiastical province of Vienna in Austria. The episcopal seat is in Eisenstadt Cathedral.
A diocese, from the Greek term διοίκησις, meaning "administration", is the district under the supervision of a bishop. A diocese is divided into parishes (in the Church of England into benefices and parishes). This structure of church governance is known as episcopal polity. The word diocesan means relating or pertaining to a diocese. It can also be used as a noun meaning the bishop who has the principal supervision of a diocese.
A diocese also may be referred to as a bishopric or episcopal see, though strictly the term episcopal see refers to the domain of ecclesiastical authority officially held by the bishop, and the term bishopric to the post of being bishop.
An archdiocese (or archiepiscopal see or archbishopric) is more significant than a diocese. An archdiocese is presided over by an archbishop whose see may have or have had importance due to size or historical significance. The archbishop may have metropolitan authority over any other suffragan bishops and their dioceses within his ecclesiastical province.