Sandøya is an island in Porsgrunn Municipality in Telemark county, Norway.

The 1.5-square-kilometre (0.58 sq mi) island lies just west of the smaller island of Løvøya and about 2 kilometres (1.2 mi) to the east of the town of Brevik.

The island lies at the mouth of the Eidangerfjorden, near where the Frierfjorden joins it to form the Langesundsfjorden.

The main urban area on the southwestern shore of the island is known as the village of Sandøya.

This Telemark location article is a stub.