The Cuban Missile Crisis, also known as the October Crisis of 1962 (Spanish: Crisis de Octubre), the Caribbean Crisis (Russian: Карибский кризис, tr. Karibsky krizis, IPA: [kɐˈrʲipskʲɪj ˈkrʲizʲɪs]), or the Missile Scare, was a one-month, four-day (16 October – 20 November 1962) confrontation between the United States and the Soviet Union which escalated into an international crisis when American deployments of missiles in Italy and Turkey were matched by Soviet deployments of similar ballistic missiles in Cuba. Despite the short time frame, the Cuban Missile Crisis remains a defining moment in U.S. national security and nuclear war preparation. The confrontation is often considered the closest the Cold War came to escalating into a full-scale nuclear war.In response to the presence of American Jupiter ballistic missiles in Italy and Turkey, and the failed Bay of Pigs Invasion of 1961, Soviet First Secretary Nikita Khrushchev agreed to Cuba's request to place nuclear missiles on the island to deter a future invasion. An agreement was reached during a secret meeting between Khrushchev and Cuban Prime Minister Fidel Castro in July 1962, and construction of a number of missile launch facilities started later that summer.

Meanwhile, the 1962 United States elections were under way, and the White House denied charges for months that it was ignoring dangerous Soviet missiles 90 mi (140 km) from Florida. The missile preparations were confirmed when an Air Force U-2 spy plane produced clear photographic evidence of medium-range R-12 (NATO code name SS-4) and intermediate-range R-14 (NATO code name SS-5) ballistic missile facilities.

When this was reported to President John F. Kennedy, he then convened a meeting of the nine members of the National Security Council and five other key advisers in a group that became known as the Executive Committee of the National Security Council (EXCOMM). During this meeting, President Kennedy was originally advised to carry out an air strike on Cuban soil in order to compromise Soviet missile supplies, followed by an invasion of the Cuban mainland. After careful consideration, President Kennedy chose a less aggressive course of action to avoid a declaration of war. After consultation with them, Kennedy ordered a naval "quarantine" on October 22 to prevent further missiles from reaching Cuba. By using the term "quarantine" rather than "blockade" (an act of war by legal definition), the United States was able to avoid the implications of a state of war. The US announced it would not permit offensive weapons to be delivered to Cuba and demanded that the weapons already in Cuba be dismantled and returned to the Soviet Union.

After several days of tense negotiations, an agreement was reached between Kennedy and Khrushchev. Publicly, the Soviets would dismantle their offensive weapons in Cuba and return them to the Soviet Union, subject to United Nations verification, in exchange for a US public declaration and agreement to not invade Cuba again. Secretly, the United States agreed that it would dismantle all of the Jupiter MRBMs, which had been deployed in Turkey against the Soviet Union. There has been debate on whether or not Italy was included in the agreement as well. While the Soviets dismantled their missiles, some Soviet bombers remained in Cuba, and the United States kept the Naval quarantine in place until November 20 of that year.When all offensive missiles and the Ilyushin Il-28 light bombers had been withdrawn from Cuba, the blockade was formally ended on November 20, 1962. The negotiations between the United States and the Soviet Union pointed out the necessity of a quick, clear, and direct communication line between the two Superpowers. As a result, the Moscow–Washington hotline was established. A series of agreements later reduced US–Soviet tensions for several years until both parties eventually resumed expanding their nuclear arsenals.