French statesman who, as the trusted minister of King Henry IV, substantially contributed to the rehabilitation of France after the Wars of Religion (1562–98).

The son of François de Béthune, Baron de Rosny, he was brought up as a Huguenot and was sent at an early age to the court of Henry of Navarre (later Henry IV of France). Taken by Henry to Paris in 1572, he barely escaped death during the massacre of Protestants on St. Bartholomew's Day. During the civil wars Rosny (as he was then called) served Henry both in battle and as a special agent and was wounded in the Battle of Ivry (1590) during Henry's struggle for the French crown. He helped to arrange Henry's marriage to Marie De Médicis (1600) and to negotiate the Peace of Savoy (1601). In 1603 he served as ambassador extraordinary to King James I of England. Although for political reasons he urged Henry to become a Roman Catholic, he refused to change his own religion.

Rosny, who became director of the king's Council of Finance in 1596, seems to have been sole superintendent of finances by 1598. As such, he stopped various abuses in tax collecting, including the raising of money by provincial governors on their own authority. He also abolished some superfluous public offices. It was he, moreover, who in 1604 sponsored the adoption of the paulette, or “annual right” (droit annuel, suggested by the financier Charles Paulet), which assured the state of a predictable revenue, although at the cost of making government offices hereditary. Under this system, officeholders, by paying annually one-sixtieth of the sum that they had originally paid for their office, could secure the right to transfer it at will.

Rosny's power eventually eclipsed that of the chancellor, Pompone de Bellièvre, who stood for the old tradition of the French monarchy. Rosny was indeed “the king's man,” subordinating private and particular interests to the authority of the state. Rosny's loyalty was copiously rewarded with offices. In 1606 he was created Duke de Sully and a peer of France.

Sully encouraged agriculture and stock raising, urged the free circulation of produce, checked the destruction of forests, promoted road building and the draining of marshland, and planned a great canal system (the Briare Canal was actually started). He strengthened the military forces and directed the construction of frontier defense works.

Sully's political role practically came to an end with the assassination of Henry IV in 1610. Though Marie de Médicis, as regent for Louis XIII, at first retained him in her council, his colleagues were restive under his domineering leadership, and in January 1611 the queen accepted his resignation. He spent the rest of his life in retirement, writing his Mémoires, otherwise known as the Économies royales (1638). These memoirs are remarkable for their often-reprinted account of the “Great Design,” which Sully attributes to Henry IV and which was a European confederation, or “Christian republic,” to be established after the defeat of Austria and Spain.