The Itanhaém Formation (Portuguese: Formacão Itanhaém) 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 reservoir rock of the Tambaú Field in the Santos Basin.

These facies change laterally into the coarse clastics of the Florianópolis Formation.

Facies analysis indicates a marine environment ranging from sub-littoral (inner neritic) and more rarely to pelagic (outer bathyal) conditions.

[2] The formation is the reservoir rock of the Tambaú Field in the Santos Basin.