Willem Barentsz (Dutch pronunciation: [ˈʋɪləm ˈbaːrənts]; c. 1550 – 20 June 1597), anglicized as William Barents or Barentz, was a Dutch navigator, cartographer, and Arctic explorer.

Barentsz went on three expeditions to the far north in search for a Northeast passage. He reached as far as Novaya Zemlya and the Kara Sea in his first two voyages, but was turned back on both occasions by ice. During a third expedition, the crew discovered Spitsbergen and Bear Island, but subsequently became stranded on Novaya Zemlya for almost a year. Barentsz died on the return voyage in 1597.

The Barents Sea, among many other places, is named for him.