Born to an unwed mother in Pusey, Fance, Courtois displayed artistic talent early in his life and began his study at the Ecole Municipale de Dessin in Vesoul. He is considered a part of the 19th century school of Vesulian painting, to which Jean-Léon Gérôme also belonged. His drawings were shown to Gérôme, who, in 1869, encouraged Courtois to attend the Ecole Nationale Supérieure des Beaux-Arts in Paris. There he met fellow student Pascal Dagnan-Bouveret, and the two shared a studio in Neuilly-sur-Seine beginning in the 1880s. Courtois taught painting at the Académie de la Grande Chaumière and the Académie Colarossi in Paris, where Georges d'Espagnat was one of his pupils.