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.

Seeking to containerize its coffee bean traffic from Venezuela, in 1960 Grace had the Santa Eliana and her sister ship Santa Leonor lengthened and widened by the Maryland Shipbuilding and Drydock Company and converted into the first U.S.-flagged, all-container ships devoted to foreign trade, with a capacity of 382 containers below-deck plus 94 on-deck.

With Grace Line's plans repeatedly frustrated by longshoremen opposition in both Venezuela and New York, the ship was sold in 1964 to the American container line Sea-Land Service and renamed SS Sea, and then SS Mayaguez (named after the city of Mayagüez on the west coast of Puerto Rico) in 1965.

[5] U.S. Marines recaptured the ship and attacked the island of Koh Tang where it was believed, in error, that the crew were being held as hostages.

Encountering stronger than expected defenses 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.