Cornelis Cornelisz., who later appropriated the name of his hometown Haarlem, was born in 1562 to the cloth merchant Cornelis Thomasz. and Alijdt Jacobsdr. During the Spanish occupation from 1572 to 1577 his parents left Haarlem, entrusting the boy with the painter Pieter Pietersz., who later became his teacher. Cornelisz. interrupted a trip to France in 1579 at Rouen, where the plague had broken out. He went to Antwerp and worked there with Gillis Coignet for a year. Around 1580 he returned to Haarlem, where Hendrick Goltzius had already settled. Together with Karel van Mander, who had lived in Haarlem since 1583, they founded an 'Academy' in the following years and thus made the city an important art centre. In 1583 Cornelisz. was given his first commission for a militia portrait, which indicates that he was already a member of the Guild of St Luke by that point. Between 1590 and 1593 he executed various commissions for the Prinsenhof. In 1600 the painter married the mayor's daughter, Maritge Arentsdr. Deyman, who died six years later. In 1605 he inherited a third of his father-in-law's estate. A relationship with Margriet Pouwelsdr. produced an illegitimate daughter born in 1611. Cornelisz. repeatedly assumed important social offices. He was one of the regents of the Oude Mannenhuis from 1613 to 1618, for example, and a member of the Catholic St James Militia from 1626 to 1629. In 1631 he was one of the signatories of a new charter for the Guild of St Luke. He died in Haarlem on 11 November 1638. Gerrit Pietersz. and Cornelis Jacobsz. Delff were among his pupils. His grandson Cornelis Bega later became a genre painter. His early work still shows Flemish influences, which were supplanted in the late 1580s by the Mannerist style set by Hendrick Goltzius and Bartholomeus Spranger.