Oleg Vladimirovich Penkovsky, codenamed HERO (Russian: Олег Владимирович Пеньковский); April 23, 1919, Vladikavkaz, North Ossetia, Soviet Russia, – May 16, 1963, Soviet Union), was a colonel with Soviet military intelligence (GRU) in the late 1950s and early 1960s who informed the United Kingdom and the United States about the Soviet Union placing missiles in Cuba, which led to the Cuban Missile Crisis.

Penkovsky's father died fighting as an officer in the White Army in the Russian Civil War. Penkovsky graduated from the Kiev Artillery Academy in the rank of lieutenant in 1939. After taking part in the Winter War against Finland and in World War II, he had reached the rank of lieutenant-colonel.

A GRU officer, Penkovsky was appointed military attaché in Ankara, Turkey in 1955. He later worked at the Soviet Committee for Scientific Research. Penkovsky was a personal friend of GRU head Ivan Serov and Soviet marshal Sergei Varentsov.

There are two very different opinions about Oleg Penkovsky. While the majority of observers seem to feel that he was a genuine defector as described in The Penkovsky Papers,Peter Wright, a scientist with MI5 in Britain, was convinced that Penkovskiy was a Soviet plant designed to lead the United States to the conclusion that the USSR's intercontinental missile capabilities were much less developed than they actually were.