Bojonegoro Regency (Indonesian: Kabupaten Bojonegoro, older spelling is Kabupaten Bodjanegara) is a regency in East Java, Indonesia, about 110 km west of Surabaya. Bojonegoro is located in the inland part of northern Java plain, on the banks of the Solo River, the longest river in Java. Previously known as a major producer of teak and tobacco, Bojonegoro is a focus of attention in Indonesia as a new oil field has been found in this area. This oil find is the biggest oil discovery in Indonesia in three decades and one of the biggest reserve in Indonesia.