From the Wikipedia page 
Sikonge District is one of the seven districts of the Tabora Region of Tanzania. The town of Sikonge is the administrative seat. The district has an area of 27,873 square kilometres (10,762 sq mi), but 26,834 square kilometres (10,361 sq mi) of it is in forest and game reserves. It is bordered to the northwest by Urambo District, to the north by Uyui District to the east by Manyoni District of Singida Region, to the south by Chunya District of Mbeya Region, and to the southwest by Mlele District of Katavi Region.