Chun Doo-hwan (Korean: ; Hanja: ; Korean pronunciation: [tnduwn] or [tn] [tuwn]; 18 January 1931 23 November 2021) was a South Korean army general and military dictator who ruled as a military strongman from 1979 to 1980 and officially as the fifth president of South Korea from 1980 to 1988. Before that he was the country's de facto leader from December 1979 to September 1980, ruling as unelected military dictator with civilian president Choi Kyu-hah largely as a figurehead.Chun usurped power after orchestrating the 12 December 1979 military coup in the aftermath of the assassination of president Park Chung-hee, who was himself another military dictator ruling since 1962. He cemented his military dictatorship in the 17 May 1980 military coup in which he declared martial law and subsequently set up a concentration camp for "purificatory education". He then established the highly authoritarian Fifth Republic of Korea on 3 March 1981. Chun would eventually concede to democratic elections as a result of the June Struggle of 1987, but was succeeded by his ally Roh Tae-woo who had been elected in the resulting December 1987 presidential election. Roh Tae-woo, a close friend of Chun, would continue many of his policies during his own rule into the 1990s.In 1996, Chun was sentenced to death for his role in the Gwangju Massacre which had led to the deaths of thousands of citizens. Chun was pardoned the following year, along with Roh Tae-woo who had been sentenced to 17 years, by President Kim Young-sam on the advice of the incoming President-elect Kim Dae-jung, whom Chun's administration had sentenced to death some 20 years earlier. Both Chun and Roh were fined $203 million and $248 million respectively, amounts that were embezzled through corruption during their regimes, which were mostly never paid.In his final years, Chun was criticized for his unapologetic stance and the lack of remorse for his actions as a dictator and his wider regime. Chun died on 23 November 2021 at the age of 90 after a relapse of myeloma.

The Coup d'état of December Twelfth (Hangul: 12.12 군사반란; Hanja: 12.12 軍事叛亂) or the "12.12 Military Insurrection" was a military coup d'état which took place on December 12, 1979, in South Korea.

Republic of Korea Army Major General Chun Doo-hwan, commander of the Security Command, acting without authorization from Acting President Choi Kyu-ha, ordered the arrest of General Jeong Seung-hwa, ROK Army Chief of Staff, on allegations of involvement in the assassination of President Park Chung Hee.

After Jeong's capture, 29th Regiment of the 9th Division, along with the 1st and 3rd Airborne Brigades, invaded downtown Seoul to support the 30th and 33rd Capital Security Group loyal to Chun, then a series of conflicts broke out in the capital. Two of Jeong's allies, Major General Jang Tae-wan (Capital Security commander) and Major General Jeong Byeong Ju (special forces commander), were also arrested by the rebel troops. Major Kim Oh-rang, Aide-de-camp of Jeong Byeong Ju, was killed during the gun-fight.

By the next morning, the Ministry of Defense and Army HQ were all occupied. Chun and his fellow 11th class of Korea Military Academy graduates, such as Major General Roh Tae-woo, commanding general of 9th Infantry Division, and Major General Jeong Ho-yong, were in charge of the Korean military. Chun was supported in the coup and the subsequent consolidation of power by the powerful private club of military officials called Hanahoe.

The Coup d'état of December Twelfth and the Coup d'état of May Seventeenth ended the Fourth Republic of South Korea and led to the establishment of the Fifth Republic of South Korea. The coup, alongside the Gwangju Massacre is the primary justification of Chun's 1995 arrest by the Kim Young-sam administration.