The Lapa oil field is a deepwater oil field in the pre-salt Guaratiba Group of the South Atlantic Santos Basin, 270 kilometres (170 mi) off the coast of São Paulo, Brazil. The field lies in water depths of approximately 2,140 metres (7,020 ft). When the discovery of the field was initially reported, it caused widespread commotion because of the speculated size of the field, which surpassed the Mexican Cantarell Complex, the biggest oil field complex outside of the Middle East. The size of Lapa, then known as Carioca and later as Sugar Loaf, was announced as possibly "as large as 33 billion barrels [5.2 billion cubic metres]". Later appraisal of the field drastically reduced the reserves to the current estimate of 459 million barrels.

The Santos Basin is an approximately 352,000 square kilometres (136,000 sq mi) large mostly offshore sedimentary basin. It is located in the south Atlantic Ocean, some 300 kilometres (190 mi) southeast of Santos, Brazil. The basin is one of the Brazilian basins to have resulted from the break-up of Gondwana since the Early Cretaceous, where a sequence of rift basins formed on both sides of the South Atlantic; the Pelotas, Santos, Campos and Espírito Santo Basins in Brazil, and the Namibia, Kwanza and Congo Basins in southwestern Africa.