Antoine Isaac, baron Silvestre de Sacy (September 21, 1758 - February 21, 1838), was a French orientalist.

He was born in Paris, his father being a notary named Silvestre, and the additional name of de Sacy was taken by the younger son after a fashion then common with the Paris bourgeoisie. From the age of seven, when he lost his father, he was educated in isolation by his mother. In 1781 he was appointed councillor in the cour des monnaies, and was advanced in 1791 to be a commissary-general in the same department. De Sacy had successively acquired all the Semitic languages, and as a civil servant he found time to make himself a great name as an orientalist. He began successfully to decipher the Pahlavi inscriptions of the Sassanid kings (1787-1791). In 1792 he retired from public service, and lived in close seclusion in a cottage near Paris till in 1795 he became professor of Arabic in the newly founded school of living Eastern languages.

The interval was in part devoted to the study of the religion of the Druze, which was the subject of his last and unfinished work, the Exposé de la religion des Druzes (2 vols., 1838). Since the death of Johann Jakob Reiske, Arabic learning had been in a backward state. In the Grammaire arabe (2 vols., 1st ed. 1810,) and the Chrestomathie arabe (3 vols., 1806), together with its supplement, the Anthologie grammaticale (1829), De Sacy supplied admirable text-books, and earned the gratitude of later Arabic students.

In 1806 he added the duties of Persian professor to his old chair, and from this time onwards his life was one of increasing honour and success, broken only by a brief period of retreat during the Hundred Days. He was perpetual secretary of the Academy of Inscriptions from 1832 onwards; in 1808 he had entered the corps législatif; he was made a baron in 1813; and in 1832, when quite an old man, be became a peer of France and was regular in the duties of the chamber. In 1815 he became rector of the University of Paris, and after the second restoration he was active on the commission of public instruction. With Abel Rémusat, he was joint founder of the Société asiatique, and was inspector of oriental types at the royal printing press.

Among his other works are his edition of Hariri (1822), with a selected Arabic commentary, and of the Alfiya (1833), and his Calila et Dimna (1816)--the Arabic version of that famous collection of Buddhist animal tales which has been in various forms one of the most populai books of the world. A version of Abd-el-latif, Relation arabe sur l'Egypte, and essays on the history of the law of property in Egypt since the Arab conquest (1805-1818). To biblical criticism he contributed a memoir on the Samaritan Arabic of the Pentateuch (Mini. Acad. des Inscr. vol. xlix.), and editions of the Arabic and Syriac New Testaments for the British and Foreign Bible Society. Of his students may be mentioned Professor Heinrich Leberecht Fleischer (1801-1888), who contributed elaborate notes and corrections to the Grammaire arabe (Kleinere Schriften, vol. i., 1885).