Jacob Denys (1644–1708) was a Flemish Baroque painter.
Denys was born and died in Antwerp. According to Houbraken he went to Rome to study the masters and spent three years copying the works of Raphael and Giulio Romano. His patrons were the Duke of Mantua, Ferdinando Gonzaga, and the Duke of Tuscany, Cosimo III de' Medici, who rewarded him with a gold chain. He painted room decorations there and in Mantua with his father, the painter Frans Denys, but when his father died he returned to Antwerp.
According to the RKD he was in Italy from 1666 to 1680. In 1679 he was back in Antwerp where he became a member of the Guild of St. Luke as "winemaster". He remained in Antwerp until 1693, and is registered in Rome in 1702. He is known for portraits and landscapes. He collaborated on a flower garland with Daniel Seghers whereby the centerpiece was by his hand of the holy family.