Jacques Auguste de Thou (Thuanus) (October 8, 1553, Paris – May 7, 1617, Paris) was a French historian, book collector and president of the Parlement de Paris.
Jacques Auguste de Thou was the grandson of Augustin de Thou, president of the parlement of Paris (d. 1544), and the third son of Christophe de Thou (d. 1582), premier président of the same parlement, who had had ambitions to produce a history of France. His uncle was Nicolas de Thou, Bishop of Chartres (1573–1598). With this family background, he developed a love of literature, a firm but tolerant piety, and a loyalty to the Crown.
At seventeen, he began his studies in law, first at Orléans, later at Bourges, where he made the acquaintance of François Hotman, and finally at Valence, where he had Jacques Cujas for his teacher and Joseph Justus Scaliger as a friend. He was at first intended for the Church; he received the minor orders, and on the appointment of his uncle Nicolas to the episcopate succeeded him as a canon of Notre-Dame de Paris.
During the next ten years he seized every opportunity for profitable travel. In 1573 he accompanied Paul de Foix on an embassy, which enabled him to visit most of the Italian courts; he formed a friendship with Arnaud d'Ossat (afterwards Bishop of Rennes, bishop of Bayeux and a cardinal), who was secretary to the ambassador. In the following year he formed part of the brilliant cortege which brought King Henry III back to France, after his flight from his Polish kingdom. He also visited several parts of France, and at Bordeaux met Michel de Montaigne. On the death of his elder brother Jean (April 5, 1579), who was maître des requêtes to the parlement, his relations prevailed on him to leave the Church, and he entered the parlement and got married (1588). In the same year he was appointed conseiller d'état. He served faithfully both Henry III and Henry IV, because they both represented legitimate authority.