Vendsyssel-Thy or Nørrejyske Ø (Danish for North Jutland Island) is the northmost part of the Jutland Peninsula (Denmark) and the second largest island of Denmark.

It is, however, seldom regarded as a single unit. It consists of three areas which are referred to much more often than to the island as a whole. The consisting areas are:

• Vendsyssel, the largest part at east and north (in North Jutland County),
• Hanherrederne in the central part (divided between North Jutland and Viborg Counties),
• Thy at west (in Viborg County, except for the southmost part, called Thyholm, in Ringkjøbing County).

Vendsyssel-Thy was once connected to the remaining part of Jutland by a 13 km long and less than 1 km wide isthmus, the Agger Tange which separated the North Sea from the Limfjord. It became an island at February 3, 1825 when a flooding made Agger Canal through the north end of the isthmus. Thyborøn Canal was created through the center of Aggertange by another flooding in 1862, and Agger Canal began to be filled with sand, and it was eventually closed in 1877, thus making the island a little bit larger.

An ancient Germanic tribe recorded in Jutland, the Vandals, may have had their original homeland in the Vendsyssel and taken their name from it.

• Area: 4,685 km²
• Population: 306,373 (January 1, 2003)
• Most important towns: Hjørring, Frederikshavn, Løkken, Lønstrup, Brønderslev, Hirtshals