island at the north end of Jutland, Denmark, known as Vendsyssel in the east and Thy in the west. The Limfjorden separates it from the mainland, to which it was attached until 1825, when water erosion cut a channel through the narrow isthmus at Thyborøn. Several bridges, ferries, and a tunnel connect the island with the rest of Jutland. It is the second largest island of Denmark, with an area of 1,809 square miles (4,685 square km). Several bridges, a road tunnel, and ferries connect the island with the rest of Jutland.

Vendsyssel is an open, windswept region with an abundance of windmills. Frederikshavn, the main port, lies on the east coast facing Göteborg, Sweden, across the Kattegat. The island's west coast, curving around the shallow, treacherous Jammerbugt (“Bay of Woe”) of the Skagerrak, is lined with white sand beaches and shifting dunes. In the 20th century many seaside vacation cottages were built among the older fishing villages along the shore. At Skagen in the extreme north, where the Kattegat and the Skagerrak meet, the dunes move perceptibly from year to year.

The Thy peninsula curves southwest from Vendsyssel to the Thyborøn channel. Dunes and drift sand, blown inland from the North Sea shore, cover a quarter of the land. Plantations of conifers and marram grass have stabilized much of the duneland for use as a wildlife sanctuary and holiday resort. Farming and fishing are limited, especially on and near the North Sea, and Thisted on the Limfjorden is the only sizable town. At Hanstholm on the North Sea, a deepwater port was opened in 1967 to accommodate fishing boats and provide employment, and new town development was projected. Pop. (2003 est.) 306,373.