Ultraløbet Ærø Route 66 is a 66 km ultramarathon circumnavigating the Danish island of Ærø, beginning in Marstal at Ærøhallen. Established in 2018, the race accommodates solo participants and relay teams of two or three, with a 10-hour cutoff.
The course utilizes the Kyststien along Ærø’s southern coast to Søby, close to Vitsø. From there, it connects with the Ø-havssti, heading back towards Marstal via the island’s northern side, passing Ærøskøbing. Participants will encounter varied terrain including asphalt, beach, trail, and hills, with some sections featuring steps over fences. Course marking relies on Ø-havssti and Kyststien signage, supplemented by tape or painted arrows at potentially confusing points. Two aid stations are positioned at approximately 24 km and 44 km, offering drinks, candy, bananas, salt, chocolate, and cake. The latter aid station also provides ham-and-cheese sandwiches. Participants must carry their own collapsible cup as disposable cups are not provided.