Ertholmene is a small archipelago in Denmark. The largest island is Christiansø, whose name is often used with reference to the entire archipelago. Ertholmene are situated 18 kilometres (11 mi) northeast of Gudhjem, Bornholm, and include Denmark's easternmost point. Two of the islands, Christiansø and Frederiksø, are inhabited, with a combined permanent population of 91. The archipelago has a total area of 39 hectares. Its name is derived from the Danish for "pea islands".

Bornholm is a Danish island in the Baltic Sea, to the east of the rest of Denmark, south of Sweden, northeast of Germany and north of Poland.