Kuusisto Castle

. Kuusisto Castle (Kuusiston piispanlinna, Kustö biskopsborg) was a medieval episcopal castle on an island of Kuusisto in Kaarina, Finland, near Turku. The castle was probably built in the early 14th century, although the site seems to have been bishop's residence already in the 1290s.

The castle was ordered to be demolished during the Protestant Reformation in 1528 by the king Gustav I of Sweden. Excavation and reconstruction work on the remaining ruins began in 1891.