Mesonauta festivus, the flag cichlid, is a species of cichlid native to the Paraná, Paraguay, Madre de Dios, Guaporé, Mamoré, Jamari and Tapajós river basins in Brazil, Peru, Paraguay and Bolivia.

[1] It can reach a standard length of 12.1 cm (4.8 in) and is sometimes kept in aquariums.

[1] It was generally recognized as the only valid species in the genus Mesonauta until 1991 when a taxonomic review found that five species should be recognized (a sixth was described in 1998).

[2][3] As a consequence aquarium specimens have generally been labelled M. festivus, but this species is seen far less often than some of its relatives, especially M. guyanae, M. insignis and M.

[4] The other species in the genus have a more northernly range than M.