Cornelis Corneliszoon van Haarlem, Dutch Golden Age painter and draughtsman, was one of the leading Northern Mannerist artists in the Netherlands, and an important forerunner of Frans Hals as a portraitist.

Born in Haarlem, Cornelis Corneliszoon was a pupil of Pieter Pietersz in Haarlem, and later Gillis Coignet in Antwerp. He is known among art historians as a member of the Haarlem Mannerists, who were highly influenced by the work of Bartholomeus Spranger, whose drawings were brought to Haarlem by Carel van Mander in 1585, and had a strong immediate effect. He painted mainly portraits as well as mythological and Biblical subjects. Initially Cornelis Cornelisz painted large-size, highly stylized works with Italianate nudes in twisted poses with a grotesque, unnatural anatomy. Later, his style changed to one based on the Netherlandish realist tradition.