Anatoliy Mikhaylovich Golitsyn (Russian: Анатолий Михайлович Голицын; 25 August 1926 – 29 December 2008) was a Soviet KGB defector and author. Born in Soviet Ukraine, he became a major in the KGB before defecting in 1961. While most of Golitsyn's information was "tantalizingly imprecise", it nonetheless proved a "treasure trove" for Western intelligence agencies investigating KGB operations and infiltrations in the west. Golitsyn's information was particularly prized by CIA counterintelligence director James Angleton, with whom he formed a close, collaborative relationship.

Golitsyn's contention, developed in the years following his defection, that the KGB had thoroughly infiltrated the intelligence agencies and governments of Western countries and that various events such as the Sino-Soviet split were elaborate disinformation operations inspired Angleton to undertake a massive molehunt within the CIA, resulting in Golitsyn's gradual marginalization and Angleton's eventual downfall. From 1965 until his death, Golitsyn focused on writing books concerning Soviet strategy. In his book Wedge: The Secret War between the FBI and CIA (Knopf, 1994), Mark Riebling stated that of 194 predictions made in New Lies For Old, 139 had been fulfilled by 1993, 9 seemed 'clearly wrong', and the other 46 were 'not soon falsifiable', an accuracy rate of almost 94%.

Golitsyn was born to lower-class parents in Pyriatyn, Soviet Ukraine in 1926. As a cadet at the Odessa-based Frunze Artillery School during World War II, he assisted in trench-digging outside of Moscow and was awarded the medal "For the defense of Moscow". At fifteen, he joined the Komsomol, and at nineteen the Communist Party of the Soviet Union. In the same year, he joined the KGB. He attended the Moscow School of Military Counter-espionage from 1945 to 1946, after which he became a desk officer in the KGB. He attended a two-year course in counterintelligence at the Higher Intelligence School from 1948 to 1950, returning to the KGB as a case officer and being transferred to the Anglo-American section in 1951. In 1952, after making suggestions for the fundamental organization of the USSR's intelligence, he allegedly had the chance to meet Joseph Stalin (a claim heavily doubted by CIA handlers). Upon Stalin's death, he was reassigned to operations monitoring Russian émigrés in Vienna, but was eventually reassigned to the Anglo-American-French group at the Vienna residency, focusing on counterintelligence. From 1955 to 1959, he completed a law course at the KGB Higher School Juridical Institute. In 1959, he became a senior case officer responsible for NATO information in Moscow, a role which led him to present reports directly to members of the Central Committee of the CPSU, including Khruschev. In order to prepare for a posting in Helsinki, he was moved to the American section in 1960. Golitsyn also claimed to have received academic qualifications from the Institute of Marxism–Leninism and the Diplomatic Academy.

In 1961 under the name "Ivan Klimov" he was assigned to the Soviet embassy in Helsinki, Finland, as vice consul and attaché. He defected with his wife and daughter to the Central Intelligence Agency via Helsinki on 15 December 1961. They flew "with a CIA escort from Finland to Sweden and thence to the United States via Frankfurt am Main, Germany, arriving on 18 December 1961". He was interviewed by James Jesus Angleton, CIA counter-intelligence director. In January 1962, the KGB sent instructions to Rezidentura throughout the world on the actions required to minimize the damage. All meetings with important agents were to be suspended. In November 1962, KGB head Vladimir Semichastny approved a plan for the assassination of Golitsyn and other "particularly dangerous traitors" including Igor Gouzenko, Nikolay Khokhlov, and Bogdan Stashinsky. The KGB made significant efforts to discredit Golitsyn by promoting disinformation that he was involved in illegal smuggling operations.

Once Golitsyn was processed and his bona fides accepted, he was given a house in McLean, Virginia where he could live with his wife, Svetlana, and daughter, Tatyana, a settlement of approximately $200,000, and guards. He was provided the false identity of "John William Stone".

Upon his defection, Golitsyn was unable to precisely identify any KGB agents outside of Helsinki to his new handlers, but provided a wide range of imprecise information, including knowledge of "Sasha", a compromised CIA asset in West Germany. Most of his information concerned the structure and management of KGB operations, recruiting, and agent-running. In the years immediately following his defection, Golitsyn was allowed privileged access to classified material from the CIA and other intelligence agencies, and frequently met (mostly at his own request) with high-ranking figures including Robert F. Kennedy and John McCone. Requests made by him to meet with Herbert Hoover and John F. Kennedy were repeatedly denied. He was "loaned out", under CIA supervision, to other western intelligence agencies for interviews. Golitsyn's contact with MI6 resulted in the final exposure of Kim Philby, while a series of interrogations with French intelligence officers resulted in the Martel affair and, indirectly, the exposure of Georges Pâques.

By February 1963, he had become increasingly uncooperative with his CIA handlers, briefly defecting to the UK before returning to the US to live in the New York City area. It was after his return to the US that he accused Harold Wilson of being a KGB agent (discussed below) and claimed that the Sino-Soviet split, which he had discussed with his handlers the year prior, was an elaborate disinformation operation. He also claimed that, to various degrees, splits between the USSR and Albania, Romania, Yugoslavia, and Hungary were disinformation operations meant to obfuscate the true extent and unity of communist power. These allegations, based on the premise that the KGB had infiltrated western governments and intelligence services and was conducting massive deception operations to undermine and defeat the west, became known as the "Monster Plot". Following Yuri Nosenko's defection in 1964 (also discussed below), he served as a "behind-the-scenes advisor" for interrogations of Nosenko, who he vehemently insisted was a KGB plant. In the next years, Golitsyn continued to be a crucial advisor to Angleton, and their theory of the "Monster Plot" would inform Angleton's discrediting of defectors Dmitri Polyakov, Aleksey Kulak, and Mikhail Klochko, a scientist who defected to Canada in 1961.

Based on Golitsyn's allegations of an expansive network of KGB moles in the CIA, Angleton embarked on an expansive molehunt in February 1964, which uncovered one mole, Igor Orlov, but also resulted in career-ending allegations for four other (innocent) CIA officers and many others. As a result of the destructive molehunt, Angleton was eventually dismissed in 1974 by William Colby. The FBI cut off contact with Golitsyn in 1965, the culmination of his gradual marginalization by the intelligence community. After 1965, excepting his contact with Angleton, Golitsyn mostly pivoted to writing books exploring his theories, and limited contact with the CIA.