Theodoric of Isenburg-Büdingen (German: Diether von Isenburg-Büdingen) (1412 - 7 May 1482) was the Archbishop of Mainz from 1459 until 1461, and again from 1475 until 1482. Theodoric was a son of Count Theodoric I of Isenburg-Büdingen. Early in childhood he was sent into a religious life. He was educated in Cologne and later Erfurt. In 1427 he became a member of the Cathedral of Mainz, in 1434 a rector in Erfurt, and in 1453 a cathedral vicar. In 1456 the cathedral chapter of Trier elected John II of Baden against Theodoric. On 18 June 1459 Theodoric was elected the Archbishop of Mainz with a clear majority over Adolph of Nassau-Wiesbaden-Idstein, however the Pope never confirmed Theodoric. In 1461 he went to Nuremberg for Imperial and Papal reform, and its recommendations earned Theodoric