Maternus of Cologne was a fourth-century Christian bishop who served as the first documented leader of the see in Cologne. He is also recognized as the third bishop of Trier and the founder of the diocese of Tongeren. Active during the era of the Donatist controversy, he participated in significant ecclesiastical gatherings, including the Synod of Arles in 314 and a meeting in Rome in 313 called by Emperor Constantine. His work was instrumental in spreading the Christian faith throughout Alsace and Western Germany.