Hesselø is a small island of Denmark, belonging to Halsnæs Municipality, in Region Hovedstaden.

In fiction, the Norwegian illustrator and author Tor Bomann-Larsen in the comic book '1905.

The Duel at Hesselø' wrote that the Swedish and Danish princes duelled here for the unoccupied Norwegian throne.

Another 'duel' occurred in 1983 when the Danish government gave permission for test-drilling for oil north-east of the island against protests from Sweden.

A new offshore wind port is scheduled to be completed off the coast of Hesselø in 2027.