Jacques Guay (1711–1793) was a French gemstone engraver, a protégé of Madame de Pompadour (1721–1764), mistress of King Louis XV of France (1710–74).

[5] After Guay returned to France the king's mistress Jeanne-Antoinette Poisson, Madame de Pompadour, an artist in her own right, installed him in her apartment in the Palace of Versailles and charged him with making engravings in gemstones of the main events and characters of the reign.

[6] Guay made an engraving on a small carnelian of the Triumph of Fontenoy after a design provided by Edmé Bouchardon.

[15] In a portrait of Madame de Pompadour by Boucher, exhibited in a Salon of 1755, papers at her feet include one of her print engravings after a cameo by Guay.

[16] A portrait of Madame de Pompadour at Her Toilette shows her wearing Guay's cameo of Louis XV on her wrist.

Guay's miniature of Louis XV, cut from three-color sardonyx, was the basis for an etching of the king as a Roman emperor by Pompadour.

There is however, at the present day, a skilful engraver in Paris of the name of Jeoffroy, whom the national institute has thought worthy to receive among its members."

[20][b] Guay's style is closer to the work of contemporary medalists and Rococo artists such as Boucher and Bouchardon than to the Roman masters of gem engraving.