The 1983 Soviet nuclear false alarm incident was a significant event that occurred during the Cold War, when the Soviet Union's early warning system incorrectly detected the launch of multiple intercontinental ballistic missiles (ICBMs) from the United States, indicating an imminent nuclear attack.

The incident occurred on September 26, 1983, during a period of high tensions between the US and Soviet Union. The Soviet Union's early warning system, which was designed to detect the launch of ICBMs, indicated that the US had launched a massive nuclear attack. The system reported that several ICBMs had been launched from the US, and that they were headed towards the Soviet Union.The Soviet military immediately went on high alert and prepared to launch a retaliatory nuclear strike.

The false alarm was caused by a malfunction in the early warning system, which was triggered by a rare alignment of sunlight on high-altitude clouds and the satellites used by the system. This caused the satellites to misinterpret the clouds as a missile launch. The alarm was eventually determined to be false by Stanislav Petrov, but not before the Soviet Union's top military leaders had prepared to launch a nuclear counterattack.

The incident was kept secret by the Soviet Union until the 1990s, but it was later revealed to the public by Russian and American leaders. The incident highlighted the dangers of the Cold War and the importance of having reliable and accurate early warning systems to prevent accidental nuclear war. It also led to changes in the Soviet Union's command and control procedures, with the creation of a “nuclear briefcase”, a device that would allow Soviet leaders to confirm or deny the launch of a nuclear attack before making a decision to launch a counterattack.