The Cambodian navy seized the American container ship SS Mayaguez in what they claimed to be Cambodian territorial waters.

The Mayaguez incident took place between Kampuchea and the United States from 12 to 15 May 1975, less than a month after the Khmer Rouge took control of the capital Phnom Penh ousting the U.S.-backed Khmer Republic. After the Khmer Rouge seized the U.S. merchant vessel SS Mayaguez in a disputed maritime area, the U.S. mounted a hastily prepared rescue operation. U.S. Marines recaptured the ship and attacked the island of Koh Tang where it was believed that the crew were being held as hostages. Encountering stronger-than-expected defences on Koh Tang, three United States Air Force helicopters were destroyed during the initial assault and the Marines fought a desperate day-long battle with the Khmer Rouge before being evacuated. The Mayaguez's crew were released unharmed by the Khmer Rouge shortly after the attack on Koh Tang began. The names of the Americans killed, including three Marines left behind on Koh Tang after the battle and subsequently executed by the Khmer Rouge, are the last names on the Vietnam Veterans Memorial.

SS Mayaguez was a U.S.-flagged container ship that is best known for its 12 May 1975 seizure by Khmer Rouge forces of Cambodia, which resulted in a confrontation with the United States at the close of the Vietnam War.