Andowyne is supposedly the name of the fantasy world where Willow takes place.
The world is populated by beings such as Fairies, Brownies, Dragons, Trolls, Cyclops and Centaurs; and others such as Nelwyns, Eborsisks and the human-like Daikini.
Not much is known about the creation, history and geography of Andowyne other than some kingdoms such as Tir Asleen and Galadoorn. One of its seas is the Sunset Ocean
The name derives from an April Fool's joke according to which a planet of that name would be a crossover between Willow and Star Wars, and the Willow movie and The Shadow War Chronicles trilogy would become part of the Star Wars canon.
The world of Willow has not been named, so "Andowyne", although created for a joke, remains the most official word on that matter.