Сен-Кантен
Decorsant was born in Saint-Quentin, Aisne, France, in 1866. He trained as a lawyer in Paris, where he attained the degree of Doctor of Law. An officer in the reserves, he thereupon broke his engagement to be married and decided to study for the priesthood in Rome. He obtained a doctorate in philosophy and theology and returned to Paris, where he was ordained on 9 July 1893 in the chapel of the Institut Catholique de Paris.