ISENBURG, DIETHER von. — Archbishop of Mainz, born in 1412, died on 7 May 1482 at Aschaffenburg. Elected archbishop of Mainz in 1459, he did not receive the confirmation of Pius II. He consequently became the driving force behind anti-Roman activity in Germany and advocated the convocation of a general council to renew the decrees of the Council of Basel. In 1462 he was compelled to renounce the archiepiscopal dignity in favor of Adolph of Nassau, who was confirmed by the Pontiff. Elected archbishop again in 1475, this time he received papal confirmation. In 1477 he founded the University of Mainz.
BIBL.: K. Menzel, D. von I., Erzbischof von Mainz, Erlangen 1868; A. Veit, D. von I., in LThK, III, col. 317, with bibliography; H. Jedin, Storia del Concilio di Trento, Italian translation, Brescia 1949, pp. 45–46. Silvio Furlani