"Saint Theodore of Octodurum (also of Sion, of Grammont; German Theodor von Sitten, locally Joder; also known as Theodulus, French Théodule, Latin Theodolus Sedunensis etc.; 4th century) is the first known bishop of Octodurum, Alpes Poeninae province (present-day Martigny, Valais, Switzerland). He is the patron saint of Valais and of the Walser. His feast day is 16 or 26 August.
He is known to have participated in the Council of Aquileia in 381, his presence being preserved on the attendance list as Theodorus Episcopus Octodorensis. He was also one of the signatories of a letter addressed by the Synod of Milan to Pope Siricius early in 390, informing him of their condemnation of the monk Jovinian and his followers.He is said to have discovered the tomb of Saint Maurice, at which place he established the Abbey of St. Maurice, Agaunum.Aloys Lütolf placed the beginning of his episcopate in the 340s, which would amount to a reign of more than forty years. At first he would not have had a fixed seat and in some sources is known as "bishop of the Helvetians"." - (en.wikipedia.org 31.01.2020)