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

When Cornelis was ten years old, his parents fled Haarlem, as the Spanish army laid siege to the city during the Eighty Years War, leaving Cornelis to be raised by the painter Pieter Pietersz, his first teacher. Later, he studied in Rouen, France and Antwerp, Belgium.

Van Haarlem received his first official commission from the city of Haarlem in 1583, a militia company portrait. He later became city painter of Haarlem and received numerous official commissions. He painted many portraits as well as mythological and Biblical subjects.

Together with Carel van Mander, Hendrick Goltzius, Cornelis van Haarlem formed the Haarlem Academy. It was a small club where nude models were drawn and artistic views were exchanged. Cornelis also played a role in reorganizing the artisans guild of St. Luke, eliminating its medieval organization and raising the status of the artists.