Iranian Hostage Crisis, a diplomatic conflict caused by the holding in captivity of United States embassy personnel by Iranian militants from November 4, 1979, to January 20, 1981. The crisis was precipitated when Mohammed Riza Pahlavi, the deposed shah, was allowed into the United States for medical treatment. Iranian militants, supported by the revolutionary government under Ayatollah Ruhollah Khomeini, seized the embassy in Tehran, took the personnel hostage, and announced that the hostages would not be released until the shah was returned to Iran to stand trial. President Jimmy Carter refused the demand and retaliated with economic sanctions and diplomatic pressure. All efforts to negotiate the release of the hostages were rebuffed.

On April 24, 1980, the United States attempted a commando raid to rescue the hostages, but the mission failed when three helicopters broke down. During the mission eight United States servicemen died in a helicopter crash. On July 27, the shah died, but Iran refused to release the hostages.

Late in 1980, negotiations between the United States and Iran made progress with Algeria acting as intermediary. Finally, on the inauguration day of Ronald Reagan as President, the 52 hostages were released after 444 days of captivity.