Dietrich of Altena-Isenberg (circa 1196 – 18 July 1226), known as Dietrich III Bishop of Münster (1218–1226).[1] He was closely involved in the preparations for the construction of St. Paul's Cathedral in Münster. On 22 July 1225, he laid the foundation stone for the Dom Church, "Neubau iuxta formam templi Marienfeldensis aedificanda".[2]
Dietrich was the son of Count Arnold of Altena from his marriage to Mathilde of Cleve, daughter of Dietrich III, Count of Cleves and Adelheid of Sülzbach.[3] Like his four younger brothers Engelbert, Philip, Bruno and Gottfried, Dietrich was destined for the church. In 1218 he succeeded the Bishop of Münster, Otto I of Oldenburg, after his death during the Fifth Crusade in Syria. In his period as bishop he was known as a mint lord. Dietrich laid the foundation stone for the completion of the new construction of the Saint Paul cathedral in Műnster on 22 July 1225. His role was abruptly cut short and continued by the chapter later that year, when his brother Frederick of Isenberg was involved in the death of their uncle Engelbert II of Berg, Archbishop of Cologne, on 27 November 1226, in Gevelsberg.[4]
Dietrich left on 1 January 1226 accompanied by prelates and three abbots of his diocese, his brother Engelbert, Bishop of Osnabrück and the Bishop of Minden on his way to Liège.[5] A trial was held there on 2 February 1226, in which he and Engelbert had to defend themselves against the charge of complicity. A commotion led to the referral of the matter to the Pope. Dietrich and Engelbert set out for Rome on 23 February 1226. On 30 April 1226, while they were still on their way back, it was already known in Cologne that the Pope had confirmed their dispensation as bishop.[6] Dietrich died on 18 July 1226 while still on the return journey. His successor was Bishop Ludolf of Holte. Dietrich’s brother Engelbert was later rehabilitated and in 1239 again became Bishop of Osnabrück. Their brother Bruno, Bishop of Osnabruck succeeded him in 1250.[7]