Cornelis Corneliszoon van Haarlem (1562 – 11 November 1638) was a Dutch Golden Age painter and draughtsman, one of the leading Northern Mannerist artists in the Netherlands, and an important forerunner of Frans Hals as a portraitist.

Initially Cornelis Cornelisz painted large-size, highly stylized works with Italianate nudes in twisted poses with a grotesque, unnatural anatomy.

When his parents fled Haarlem, as the Spanish army laid siege to the city in 1573 during the Eighty Years' War, Cornelis Cornelisz remained behind and was raised by the painter Pieter Pietersz the Elder, his first teacher.

Later, in 1580–1581 Corneliszoon studied in Rouen, France, and Antwerp (with Coignet), before returning to Haarlem, where he stayed the rest of his life.

[2] Corneliszoon also played a role in the failed attempt to make a new charter for the Haarlem Guild of St. Luke in 1630, which tried to raise the status of the artists.