French Jesuit scholar who edited numerous secular and ecclesiastical works, most notably the texts of the councils of the Christian church.

Hardouin entered the Society of Jesus in 1666 and was professor of positive theology in the Jesuit Collège Louis-le-Grand at Paris (1683–1718) when he published his first works, editions of the classical writers Pliny and Themistius. Though a man of great learning, Hardouin developed strange theories and dismissed works that contradicted his opinions: he came to believe that most of the writings of Greek and Latin antiquity were medieval forgeries (forgery) executed by a conspiracy of monks.

After the unauthorized publication in Amsterdam of his Opera Selecta (1708; “Selected Works”), Hardouin was compelled publicly to disavow the theory of a forged antiquity, but a similar theory appeared in his masterwork. This was his edition of the texts of the church councils, from New Testament times onward, Conciliorum Collectio Regia Maxima: Acta Conciliorum. . . . One of the notable works of scholarship of the period, it transformed the study of canon law and was basic to all later work in the field. It was published in 12 volumes at Paris (1714–15) but was withheld for several years by the French government because of the Ultramontanism (an emphasis on papal authority and centralization of the church) displayed in the notes.

Because of his unorthodox theories, especially concerning the New Testament, which he believed had been written originally in Latin, three of his works were condemned by the church after his death.