South Korean media say former President Chun Doo-hwan died on Tuesday. He was 90.
Yonhap news agency and other outlets say Chun passed away at home in the capital, Seoul, in the morning.
The general-turned politician seized power in a 1979 military coup following the assassination of then President Park Chung-hee.
Chun was inaugurated as president the following year. He ruled the country with an iron fist until 1988.
He ordered a deadly crackdown on a pro-democracy movement led by students in the southwestern city of Gwangju in 1980.
Chun promoted the hosting of the Seoul Olympics in 1988, when the South Korean economy experienced high levels of growth.
Chun met harsh criticism over the coup and the Gwangju uprising after he stepped down as president.
The former president was arrested in 1995. He was sentenced to life in prison but pardoned in 1997.