The Olowo of Owo, Oba Folagbade Olagbegi, in Ondo State, has died at the age of 77.
A palace source said the monarch died of health complications on returning home after a security summit held in the town on Tuesday.
The traditional ruler ascended the throne in 2003.
Ondo State Government is yet to make an official statement on the incident.
The state governor, Oluwarotimi Akeredolu, a native of Owo, is said to be out of the country on official engagement.
Oba Olagbegi studied as a lawyer and also taught law.
A recipient of Commander of the Federal Republic (CFR) national award, the monarch was appointed Chancellor, University of Benin (UNIBEN) in 2015 and later University of Abuja.
He was a former Chairman, Ondo State Council of Obas.