Ixtoc 1 was an exploratory oil well being drilled by the semi-submersible drilling rig Sedco 135 in the Bay of Campeche of the Gulf of Mexico, about 100 km (62 mi) northwest of Ciudad del Carmen, Campeche in waters 50 m (164 ft) deep. On 3 June 1979, the well suffered a blowout resulting in the largest oil spill in history at its time. To-date, it remains the second largest oil spill in history after the Deepwater Horizon oil spill.

The Bay of Campeche, or Campeche Sound, is a bight in the southern area of the Gulf of Mexico, forming the north side of the Isthmus of Tehuantepec. It is surrounded on three sides by the Mexican states of Campeche, Tabasco and Veracruz. The area of the bay is 6,000 square miles (16,000 km2) and maximum depth of the bay is approximately 180 feet (55 m). It was named by Francisco Hernández de Córdoba and Antón de Alaminos during their expedition in 1517.