Jang Song-thaek (January or February 1946^{[unreliable source?]} – 12 December 2013) was a North Korean politician. He was married to Kim Kyong-hui, the only daughter of North Korean premier Kim Il Sung and his first wife Kim Jong Suk, and only sister of North Korean general secretary Kim Jong Il. He was therefore the uncle of the current leader of North Korea, Kim Jong Un, by marriage.

The extent of Jang Song-thaek's power and position has not been confirmed in the West. However, in 2008 South Korean government officials and academic North Korea experts suggested that he had de facto leadership over North Korea while Kim Jong Il's health was declining and when Kim subsequently died. Jang was a vice-chairman of the National Defence Commission, a position considered second only to that of the supreme leader. He is believed to have been promoted to four-star general around the time of Kim Jong Il's death in December 2011, as his first appearance in uniform was while visiting Kim lying in state. Jang was considered a "key policy adviser" to Kim Jong Un.

In December 2013, Jang was abruptly accused of being a counter-revolutionary and was stripped of all his posts and expelled from the Workers' Party of Korea (WPK). His photos were removed from official media and his image digitally removed from photos with other North Korean leaders. On 13 December, North Korean state media announced he had been executed by firing squad.

Jang was born in Chongjin, during the Soviet Civil Administration of Northern Korea. He graduated from the Kim Il Sung Senior High School before leaving for Moscow, where he studied at Moscow State University between 1968 and 1972. Following his return, he married Kim Kyong-hui, the younger (and only) sister of Kim Jong Il. The couple had a daughter, Jang Kum-song (1977–2006), who lived in Paris as an international student; she refused an order to return to Pyongyang and then reportedly committed suicide in September 2006, due to Jang and his wife's opposition to her relationship with her boyfriend.

Beginning in the 1970s, Jang held a series of positions in the Workers' Party of Korea (WPK). His first post was as an instructor for the Pyongyang City Committee of the Workers' Party. In the late 1970s, however Jang's career stalled when he was sent away from the central party to be manager of a steel and ironworks in Nampo, an apparent demotion. Reports said that he was becoming too powerful or, according to other accounts, he had an over-ostentatious lifestyle. It was reported that Jang suffered severe burns in an industrial accident at the factory in Chollima/Kangson. His career recovered and he became deputy director of the Youth Work Department of the 6th WPK Central Committee in 1982 and director in 1985. He was first elected to the Supreme People's Assembly (SPA), North Korea's nominal parliament, in 1986.

In April 1989, Jang was made a People's Hero; in June 1989, he was elected an alternate member of the 6th Central Committee of the Workers' Party of Korea. In April 1992, he was named a member of the Order of Kim Il Sung. Later that year he was promoted to full member of the 6th Central Committee. He was a member of the funeral committee for Kim Il Sung in 1994. Jang was appointed to be the first deputy director (or vice director) of the WPK's Organization and Guidance Department in November 1995. He had been identified by outside analysts as well as North Korean defector and former high official Hwang Jang-yop as a possible successor to Kim Jong Il; however, on 25 November 2004, South Korea's National Assembly heard testimony that he had been purged from his position. Some South Korean intelligence reports indicated that Jang was under house arrest in Pyongyang, while others suggested he might have been sent for "reeducation".

Korean Central News Agency on 29 January 2006 found that Jang had been reinstated in December 2005. At the time of the restoration, North Korean media reported that he was not the first deputy director of the organizing leadership of the Party Central Committee, but merely the first deputy director of the Party Central Committee. It is said that he was reinstated as the first deputy director of the Capital Construction Department. In 2005 and in September 2006, Jang was involved in auto accidents, the first leaving him hospitalized for five months. In one of the collisions his car was hit by a military truck, and there were rumors of an assassination plot. Jang re-emerged in March 2006, accompanying Kim Jong Il on an official visit to China. In October 2007, the Korean Central News Agency confirmed that Jang had been promoted to the newly recreated post of first vice-director of the Workers' Party of Korea, with oversight responsibility for the police, judiciary, and other areas of internal security; Jang attended South Korean president Roh Moo-hyun's luncheon during the latter's visit to the North. It was later revealed that Jang had been actually appointed director of the Administration Department, an old agency of the Workers' Party abolished in 1990 and re-created by splitting the Organization Department. He was elected to the National Defence Commission (NDC) in April 2009. He was made vice-chairman of the commission in summer 2010.

During this period he was a close ally of Kim Jong Il. Jang was still in the post four years later, in April 2013. The NDC was North Korea's de facto supreme decision-making body; Jang's promotion made him a key executive deputy, second only to Kim Jong Il. It is speculated that the move was part of posturing to make Kim Jong Il's son Kim Jong Un the next leader of North Korea. Jang's position in North Korean politics was also ostensibly boosted by the death of Ri Je-gang, a senior leader who was tipped by Kim Jong Il as a crucial overseer of the succession campaign.