General Chun Doo-hwan of South Korea seizes control of the government and declares martial law in order to suppress student demonstrations.

The Coup d'tat of May Seventeenth was a military coup d'tat carried out in South Korea by General Chun Doo-hwan and Hanahoe that followed the Coup d'tat of December Twelfth.

On May 17, 1980, General Chun Doo-hwan forced the Cabinet to extend martial law to the whole nation, which had previously not applied to Jeju-do. The expanded martial law closed universities, banned political activities and further curtailed the press. To enforce the martial law, troops were dispatched to various parts of the nation. On the same day, the Korean Central Intelligence Agency (KCIA) raided a national conference of student union leaders from 55 universities. About 2,700 people, including twenty-six politicians, were also arrested. On May 18, 1980, citizens of Gwangju rose up against Chun Doo-hwan's military dictatorship and took control of the city. In the course of the uprising, citizens took up arms to defend themselves, but were ultimately crushed by the army (see Gwangju Uprising).

On May 20, 1980, Chun Doo-hwan and Roh Tae-woo ordered the National Assembly to be dissolved by deploying troops in the National Assembly. Chun subsequently created the National Defense Emergency Policy Committee, and installed himself as a member. On July 17, 1980, he resigned his position of KCIA Director, and then held only the position of committee member. In September 1980, President Choi Kyu-hah was forced to resign from president to give way to the new military leader, Chun Doo-hwan.

Chun Doo-hwan (Korean: 전두환; Hanja: 全斗煥; Korean pronunciation: [tɕʌnduɦwɐn] or [tɕʌn] [tuɦwɐn]; 18 January 1931 – 23 November 2021) was a South Korean army general and military dictator who served as the fifth president of South Korea from 1980 to 1988.

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 would eventually usurp power for himself 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.

He cemented his military dictatorship in the 17 May 1980 military coup in which he declared martial law, set up a concentration camp for "purificatory education", and then established the highly authoritarian Fifth Republic of Korea on 3 March 1981. Chun would eventually concede for 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, 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 led to the deaths of thousands of citizens, but was along with Roh, who was sentenced to 17 years, pardoned the following year by President Kim Young-sam, on the advice of then-President-elect Kim Dae-jung, whom Chun's administration had sentenced to death some 20 years earlier. Both Chun and Roh was however fined $203 million and $248 million respectively, amounts that was embezzled through corruption under their regimes, which was mostly never indemnified.In his final years, Chun was criticized for his unapologetic stance and the lack of remorse for his actions as dictator. Chun died on 23 November 2021 at the age of 90 after a relapse of myeloma.