The Frisian Islands, also known as the Wadden Islands or the Wadden Sea Islands, form an archipelago at the eastern edge of the North Sea in northwestern Europe, stretching from the northwest of the Netherlands through Germany to the west of Denmark. The islands shield the mudflat region of the Wadden Sea from the North Sea.

The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium and France. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Sea in the north. It is more than 970 kilometres (600 mi) long and 580 kilometres (360 mi) wide, covering 570,000 square kilometres (220,000 sq mi).