Jacques Guay (1711–93) was a French gemstone engraver, a protégé of Madame de Pompadour (1721–1764), mistress of King Louis XV of France (1710–74). He was the most eminent gemstone engraver of his time, the official engraver of the king, and produced many cameo and intaglio engravings in semi-precious stones such as onyx, jasper and carnelian. Subjects included classical figures, events in the reign of the king and portraits of members of the court.