He was educated at the École des Chartes, and became successively keeper of the archives of the départment of Haute-Marne and of the imperial archives at Paris under the empire. In 1871 he became professor of palaeography at the École des Chartes. He was elected member of the Academy of Inscriptions in 1887, and became chief of the historical section of the national archives in 1893.
León Gautier rendered great services to the study of early French literature, the most important of his numerous works on medieval subjects being a critical text (Tours, 1872) with translation and introduction of the Chanson de Roland, and Les Epopées françaises (3 vols., 1866-1867; 2nd ed., 5 vols., 1878-1897, including a Bibliographie des chansons de geste).