Willem Gillisz Kool (1608 – 1666), was a Dutch Golden Age painter. He was born in Haarlem and entered the Haarlem Guild of St. Luke in 1638. In the same year he married Cornelia van der Molen, daughter of Jan Gerritsen van der Molen, on 17 januari 1638. He is well known for beach scenes. Several musea, like the Frans Hals Museum in Haarlem and the Hermitage in St. Peterburgs have paintings of Kool in their collection.