Tonj is a town situated in the Bahr el Ghazal region of South Sudan, specifically within Warrap State. The settlement is known by several different names, including Kalkuel, Genanyuon, Jurkatac, Madiera, Genngeu, and Tonjdit.
The town is bordered by the locations of Rumbek, Cueibet, Yambio, Bentiu, and Gogrial. As of 2010, the population of Tonj was recorded at 17,340 residents.