He was born in Vaureilles, Pachins, in France. His family were farmers. His first baptismal name was Gabriel; but he used his second one, François, to avoid confusion with a classmate (no relation) who was also named Gabriel Marty. Educated at the Seminary of Rodez and the Catholic Institute of Toulouse, he received ordination to the priesthood on 28 June 1930, in Rodez. He worked as a pastor in the diocese of Rodez from 1930 until 1951, and then served as vicar general of the diocese to 1952.