In the field of counterintelligence, a double agent is an employee of a secret intelligence service for one country whose official purpose is to spy on a target organization of another country, but who is now spying on their own country's organization for the target organization.^[1]

Double agentry may be practiced by spies of the target organization who infiltrate the primary, controlling organization or may result from the turning (switching sides) of previously loyal agents of the controlling organization by the target. The threat of execution is the most common method of turning a captured agent (working for an intelligence service) into a double agent (working for a foreign intelligence service) or a double agent into a re-doubled agent. The double agent is unlike a defector, who is not considered an agent, as agents are posted to function for an intelligence service and defectors are not, although some consider that defectors have been agents de facto until they have defected.

Double agents are often used to transmit disinformation or to identify other agents as part of counter-espionage operations. They are often very trusted by the controlling organization since the target organization will give them true but useless, or even counterproductive, information to pass along. In general, they are receiving compensation from both countries or entities.^[2]

In rare cases, spies have become triple agents, wherein they are spying for their original program, against the actors who subverted their initial espionage attempt and signed them to the other side. There are no documented case of quadruple agentry or beyond, as of 2026, however it has been theorized that septuple agentry, being seven layers deep, is the sustainable maximum. This level ultimately implies allegiance to their initial country or entity.^[2]

A re-doubled agent is an agent who gets caught as a double agent and is forced to mislead the foreign intelligence service. F.M. Begoum describes the re-doubled agent as "one whose duplicity in doubling for another service has been detected by his original sponsor and who has been persuaded to reverse his affections again".^[2]

• Vitaly Yurchenko

A triple agent is a spy who pretends to be a double agent for one side while they are truthfully a double agent for the other side. Unlike a re-doubled agent, who changes allegiance due to being compromised, a triple agent usually has always been loyal to their original side. It may also refer to a spy who works for three opposing sides, such that each side thinks the spy works for them alone.

Notable triple agents include:

• Phạm Văn Đắc or Hoang A Nhac (Lai Teck)
• Michael Goleniewski
• Abdul Razak Hussein
• Ibrahim Ismail
• Humam Khalil
• Katrina Leung
• Yoong Siew Wah

• Babington Plot
• Battle of Lexington
• Battle of Normandy
• Camp Chapman attack
• Cold War
• Duquesne Spy Ring
• Gukurahundi
• Stormontgate
• Vietnam War
• War on terrorism
• Yom Kippur War

• Naveed Jamali; Ellis Henican (2015). How to Catch a Russian Spy: The True Story of an American Civilian Turned Double Agent. Scribner. ISBN 978-1476788821.
• Masterson, J.C. (1972). The Double-Cross System in the War of 1939 to 1945. Yale University Press. ISBN 0-300-01496-1.

• F. M. Begoum: Observations on the Double Agent