Bjerkøya is a populated island in Holmestrand Municipality in Vestfold county, Norway. The 0.8-square-kilometre (200-acre) island lies in the Ytre Oslofjord, near the mouth of the Drammensfjorden. It lies about 4 kilometres (2.5 mi) to the north of the town of Holmestrand in a small group of islands including Kommersøya, Killingholmen, and Langøya. Bjerkøya is connected to the mainland by a 600-metre (2,000 ft) long causeway bridge on the north end of the island. The island was formerly part of the old Sande Municipality until 1 January 2020 when it became part of Holmestrand Municipality.