Belene Island (Bulgarian: остров Белене, ostrov Belene) or Persin Island (остров Персин, ostrov Persin) is the biggest island in Bulgarian waters. The island is formed by the Danube River splitting into two branches passing north and south of it. The international frontier between Bulgaria and Romania follows the north branch of the river and therefore Belene Island is part of the Bulgarian territory. The island is 14.5 kilometres (9.0 mi) long and reaching 6 km (3.7 mi) in width; it is located in the Danube, north of the town of Belene. Belene Island is the fourth biggest Danube island: during an average tide it is 41.078 square kilometres (15.860 sq mi) in area.