Iseyin is a town located in Oyo, Nigeria. It is approximately 100 km north of Ibadan. The town was estimated to have a population of 236,000, ac…Iseyin is a town located in Oyo, Nigeria. It is approximately 100 km north of Ibadan. The town was estimated to have a population of 236,000, according to United Nations 2005 estimate, which increased to 362,990 in 2011, and has a total land mass of 2,341 km². Its inhabitants are mostly of Yoruba origin and its ruler is the Aseyin of Iseyin, with the current being Oba Sefiu Oyebola Adeyeri III, Ajirotutu I.