Which lake on Zealand is Denmark's largest lake by area?

Arresø is Denmark’s largest lake by area, located on the island of Zealand.

The lake covers roughly 40.7 square kilometres and lies about 43 kilometres northwest of Copenhagen. Its shores span the municipalities of Gribskov, Halsnæs and Hillerød, with the towns of Ølsted and Frederiksværk nearby.

Arresø was once a fjord connected to Kattegat. After land rose following the last Ice Age, the former marine inlet became an enclosed lake. Today, the lake drains through the artificial Arresø Canal into Roskilde Fjord; construction began around 1717 under royal orders and involved Danish soldiers and Swedish prisoners of war.

Esrum Lake is a frequent source of confusion because it is also on Zealand and is Denmark’s second-largest lake. Furesø and Mossø are important Danish lakes too, but neither matches Arresø’s surface area.