Gunthar 1 was an archbishop of Cologne; Gunthar 1 and Theutgaud 1, the archbishop of Trier ("Theutgaudum Treverensem et Guntharium Coloniae Agrippinae archiepiscopos"), together with the bishop of Bergamo, Hagano 1, and other unnamed bishops, allowed king Lothar II (Lotharios 2) to divorce his wife Theutberga 1 and to marry his mistress Waldrada 1, to the anger of the bishop of Rome, Nicolas I (Nikolaos 28); they defended their action at a Council called at Metz (in June 863) by envoys of Nikolaos 28, and then visited Rome to defend themselves before Nikolaos 28 in person, but after inspection of documents which they produced in their defence Nikolaos 28 judged them to have exceeded their authority; they were condemned at a Council held in the Lateran palace for permitting the divorce of the king, overturning the papal excommunication of Ingiltrudis 1 and falsifying a letter written by the pope; they were then deprived of their priesthood and deposed: Lib. Pont. 107. 45-49.

Bishop Hagano 1, who had aided them in drawing up various documents, was also deposed: Lib. Pont. 107. 50. The divorce was permitted at Councils held in 860 and the marriage of Lotharios 2 to Waldrada 1 was allowed at a Council held in 862; for these and other dates, see Duchesne, Lib. Pont. II, p. 170, notes 41-45. See also Hincmar, Annals (Annales Bertiniani), s.a. 864 (PL 125, 1216ff.) (for the violent outcome of these events at Rome, ending with the removal from office of Theutgaud 1 and Gunthar 1) and s.a. 867 (PL 125, 1236) (they returned to Rome hoping to regain office, but Theutgaud 1 died and Gunthar 1 barely survived). An opponent of the see of Rome, in 861 he submitted to pope Nicolas I (Nikolaos 28) but in 864, with Ioannes 315 (of Ravenna) and Theutgaud 1 (of Trier) and others he resumed hostilities: see on this Mansi XV 597-606. 147-153 and cf. above.

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