The Guarujá Formation (Portuguese: Formacão Guarujá) is a geological formation of the Santos Basin offshore of the Brazilian states of Rio de Janeiro, São Paulo, Paraná and Santa Catarina.

The formation is the second-most important post-salt reservoir rock of the Santos Basin.

The Guarujá Formation is 832 to 2,500 metres (2,730 to 8,202 ft) thick,[1] and consists of oolitic calcarenites, which laterally grade to greyish ochre and brownish grey calcilutites and grey marls.

The microfacies indicate a tidal flat to shallow lagoon and open carbonate platform depositional environment.

The age based on planktonic foraminifera and pollen is Early Albian.