It was founded in 304, promoted in 780 to Metropolitan Archbishopric of Mainz and demoted back in 1802 to bishopric.
[4] Under Article 14 of the Reichskonkordat of 1933, which remains in force, the determination of the bishop to head the episcopal see and the composition of the chapter are governed by the provisions of Baden Concordat of 1932.
[5] Pastoral units on the parish level have been introduced as a result of a profound structural change in the Catholic Church in Germany in many dioceses, the constitution of these units was determined by particular law [law of a particular region or territory], i.e., allowing for differences from one diocese to another.
The most important educational institution of the Diocese is the Catholic University of Applied Sciences, Mainz.
In addition, there are at University of Giessen, the Institute for Catholic theology and their didactics, which is located at the Department of History and Cultural Studies.