In politics, a defector is a person who gives up allegiance to one state in exchange for allegiance to another, in a way which is considered illegitimate by the first state.^[1] More broadly, it involves abandoning a person, cause, or doctrine to which one is bound by some tie, as of allegiance or duty.^[2][3]

This term is also applied, often pejoratively, to anyone who switches loyalty to another religion, sports team, political party, or other rival faction. In that sense, the defector is often considered a traitor by their original side.^[4][5]

The physical act of defection is usually in a manner which violates the laws of the nation or political entity from which the person is seeking to depart. By contrast, mere changes in citizenship, or working with allied militia, usually do not violate any law.

For example, in the 1950s, East Germans were increasingly prohibited from traveling to the western Federal Republic of Germany where they were automatically regarded as citizens according to Exclusive mandate. The Berlin Wall (1961) and fortifications along the Inner German border (1952 onward) were erected by Communist German Democratic Republic to enforce the policy. When people tried to "defect" from the GDR they were to be shot on sight. Several hundred people were killed along that border in their Republikflucht attempt. Official crossings did exist, but permissions to leave temporarily or permanently were seldom granted. On the other hand, the GDR citizenship of some "inconvenient" East Germans was revoked, and they had to leave their home on short notice against their will. Others, like singer Wolf Biermann, were prohibited from returning to the GDR.

During the Cold War, the many people illegally emigrating from the Soviet Union or Eastern Bloc to the West were called defectors. Westerners defected to the Eastern Bloc as well, often to avoid prosecution as spies. Some of the more famous cases were British spy Kim Philby, who defected to Russia to avoid exposure as a KGB mole, and 22 Allied POWs (one Briton and twenty-one Americans) who declined repatriation after the Korean War, electing to remain in China.

When the individual leaves his country and provides information to a foreign intelligence service, they are a HUMINT source defector. In some cases, defectors remain in the country or with the political entity they were against, functioning as a defector in place. Intelligence services are always concerned when debriefing defectors with the possibility of a fake defection.

• Paquito D'Rivera, Cuban saxophonist and clarinetist, who defected to the United States in 1980.
• Mikhail Baryshnikov, Soviet (Russian) dancer, who defected to Canada in 1974, while in Toronto, touring with the Kirov Ballet.^[6] He later moved to the United States.
• Natalia Makarova, Soviet (Russian) dancer, who defected while in London in 1970.
• Georgi Markov, Bulgarian author, who defected in 1968, eventually settling in London, England.
• Rudolf Nureyev, Soviet (Russian) dancer, who defected while in Paris touring with the Kirov Ballet in 1961.^[7]
• George Balanchine, Russian choreographer, who defected to the Weimar Republic in 1924.
• Arturo Sandoval, Cuban trumpeter, pianist, and composer, who defected to the United States in 1990.
• Jan Sobota, Czech fine bookbinder, who defected to Switzerland in 1982, and settled in the United States in 1984.

• Guillermo Rigondeaux, Cuban professional boxer, who defected to the United States in 2009.
• Aroldis Chapman, Cuban baseball pitcher, who defected to Andorra in 2009 before signing a Major League Baseball contract in 2010.
• José Fernández, Cuban baseball player, who defected to the United States in 2008.
• Lutz Eigendorf, an East German football player for BFC Dynamo who defected to West Germany in 1979.
• Orlando Hernandez, Cuban baseball pitcher, who defected to the United States in 1997.
• Nadia Comăneci, Romanian Olympic Gymnast, who defected to the United States in 1989.
• Alexander Mogilny, Soviet (Russian) Hockey Player, who defected to the United States in 1988. He was the first Soviet player to defect to play in the NHL.
• Béla Károlyi and his wife Márta Károlyi, Hungarian gymnastics coaches (of Nadia Comăneci and Mary Lou Retton among others), who defected to the United States in 1981.
• Osvaldo Alonso, Cuban soccer player, who defected to the United States in 2007.
• Kimia Alizadeh, Iranian taekwondo player, who defected to the Netherlands in 2020.

• Igor Gouzenko, a Soviet cipher clerk who defected to Canada and released information regarding Soviet espionage activities in western society. Credited as one of the triggering factors for the beginning of the Cold War.
• Ion Mihai Pacepa, a Romanian Securitate general who defected to the United States from the Socialist Republic of Romania in 1978.
• Genrikh Lyushkov, the NKVD chief in the Russian Far East, defected to Manchukuo in 1938 under Great Purge and then cooperated with Imperial Japanese Army.
• No Kum-Sok (later Kenneth Rowe) is known for having been a lieutenant in the North Korean Air Force during the Korean War who defected to South Korea. On September 21, 1953, he flew his MiG-15 to the Kimpo Air Base in South Korea, claiming that he wanted to get away from the "red deceit" and is often associated with Operation Moolah.^[8]
• Heng Samrin, a top-brass military figure in Democratic Kampuchea defected to Vietnam during the Khmer Rouge purges of the Eastern Zone after considering the fate of So Phim, his superior in command.^[9]
• Riad al-Asaad, founder of the Free Syrian Army and the entire Tlass Family during the Syrian civil war
• Viktor Belenko, a Soviet Air Force lieutenant who flew a MiG-25 fighter to Japan in 1976 and gained political asylum in the United States.^[10]
• Larry Allen Abshier, the first of six American soldiers to defect to North Korea between the years 1962–1982. He died in 1983 from a heart attack while residing in Pyongyang.
• Benedict Arnold‚ a colonial general who during the American Revolutionary War defected to the British Army.
• Matiur Rahman, a Pakistani pilot who in 1971 attempted to defect with a T-33 aircraft to India to join the Bangladesh Liberation War. Flt.Lt Rashid Minhas, also on board the plane struggled with him to control the plane, which crashed killing both pilots.
• Leamsy Salazar, former lieutenant colonel of Bolivarian Navy of Venezuela and head of security detail for Hugo Chávez, defected to United States in December 2014

• Guy Burgess, British diplomat and member of the Cambridge Five, defected to the Soviet Union in 1951
• Donald Maclean, British diplomat and member of the Cambridge Five, defected to the Soviet Union in 1951
• Viktor Korchnoi, Russian chess Grandmaster, defected in Amsterdam in 1976.
• Kim Philby, British intelligence officer and member of the Cambridge Five, defected to the Soviet Union in 1963
• Walter Polovchak, minor, defected to the United States in 1980 at 12. He and his parents moved to the United States from Soviet Ukraine in 1980 but later that year his parents decided to move back to Ukraine. He did not wish to return with them and was the subject of a five-year struggle to stay permanently. He won the right to permanent sanctuary in 1985 upon turning 18.
• Viktor Suvorov (born 1947), Russian writer and former Soviet military intelligence officer who defected to the United Kingdom in 1978.
• Thae Yong-ho, a former North Korean diplomat for Britain. At an unknown date Thae defected from North Korea for his family, because he "didn't want his children, who were used to life of freedom, to suffer life of oppression". Being one of North Korea's elite, for the nation he was the highest profile defection since No Kum-sok (above) in 1953.

• Sociological definitions of apostasy
• List of baseball players who defected from Cuba
• List of American and British defectors in the Korean War
• List of Cold War pilot defections
• List of Soviet and Eastern Bloc defectors
• North Korean defectors
• Eastern Bloc emigration and defection
• Martin and Mitchell defection
• Nevozvrashchentsy
• Treason
• Turncoat
• Free Syrian Army
• Dissident
• Religious conversion

• Brook-Shepherd, Gordon. The storm petrels: the first Soviet defectors, 1928-1938. HarperCollins, 1977).
• Hänni, Adrian, and Miguel Grossmann. "Death to traitors? The pursuit of intelligence defectors from the Soviet Union to the Putin era." Intelligence and National Security (2020): 1-21.
• Krasnov, Vladislav. Soviet defectors: The KGB wanted list (Hoover Press, 2018).
• Riehle, Kevin P. "The Defector Balance Sheet: Westbound Versus Eastbound Intelligence Defectors from 1945 to 1965." International Journal of Intelligence and CounterIntelligence 33.1 (2020): 68-96.
• Riehle, Kevin P. "Early Cold War evolution of British and US defector policy and practice." Cold War History 19.3 (2019): 343-361. [ online free]

• Famous Defectors - slideshow by Life magazine
• Iranian diplomats defect^{[permanent dead link]}