Jøa is an island in the municipality of Fosnes in Nord-Trøndelag county, Norway. The island lies on the south side of the Foldafjord between the mainland and the island of Otterøya. The island is partially forested with the southern part being flat and marshy and the northern part being more mountainous. The tall Moldvikfjellet is the highest point on the island.
The Norwegian writer Olav Duun was born in the village of Dun in the central part of the island. Also in Dun is the main church for the area, Dun Church. Also, Fosnes Chapel is located on the northeastern coast of the island at the site of the old church and graveyard.