The Tupi oil field is a large oil field located in the Santos Basin, 250 kilometres (160 mi) off the coast of Rio de Janeiro, Brazil. The field was originally nicknamed in honor of the Tupi people and later named after the mollusc, however it was also ambiguously similar to the name of former Brazilian president Luiz Inacio Lula da Silva. It is considered to be the Western Hemisphere's largest oil discovery of the last 30 years.

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.