Vladimir Yefimovich Semichastny (Russian: Владимир Ефимович Семичастный, 15 January 1924 – 12 January 2001) was the head of the KGB from November 1961 to April 1967 and prior to that in 1958-59 he headed Komsomol as the first secretary of the Central Committee.

His mentor and predecessor was Alexander Shelepin. In October 1963, Semichastny sanctioned the arrest of Professor Frederick Barghoorn of Yale University when he was visiting Moscow. Semichastny hoped that by charging Barghoorn as a spy he could induce the United States to release Igor Ivanov, arrested by the Federal Bureau of Investigation that month for espionage.

Barghoorn was a personal friend of President John F. Kennedy, who forcefully stated that Barghoorn was not involved in any illegal activities at a press conference. The Soviets subsequently released Barghoorn. Ivanov was allowed to leave the United States in 1971.

Subsequently, Semichastny participated in the ouster of Soviet leader Nikita Khrushchev in October 1964, an act that undoubtedly led to his being retained by the new Soviet leadership. There are some indications that Leonid Brezhnev, who led the coup against Khrushchev, wanted to assassinate him, but Semichastny refused to allow KGB participation.

During his tenure Semichasnty attempted to create a new public image of the KGB, permitting an article to appear in the newspaper Izvestia that included an article with "a senior KGB officer" (himself); in the article he stated

"many young Communist Party and Communist Youth League workers have joined the KGB and none of the people who, during the time of the personality cult of Joseph Stalin, took part in the repressions against innocent Soviet people is now in the Service."

More articles and books on the security organs appeared, and Soviet spies became heroes in print — Rudolf Abel, Gordon Lonsdale, Harold (Kim) Philby, and Richard Sorge.

Brezhnev finally replaced Semichastny on 18 May 1967, as part of a Kremlin power shuffle. Yuri Andropov became the new chief of the KGB.