Sultan of Oman Qaboos bin Said al Said died at the age of 79, announced early on Saturday by the state media in the region.
Omani News Agency, citing official sources in the capital Muscat, said the sultan passed away late Friday afternoon.
He had ruled the country in recent weeks after a peaceful coup since 1970, and had been outside of Oman for treatment.
The funeral procession will take place on Saturday and, according to official sources, he will be buried in the family cemetery.
It will hold three days of national mourning and the Omani flag will be half hoisted for 40 days, it has been announced.