Ptychochromis grandidieri is a species of cichlid in the family Cichlidae. It is endemic to river basins along a large part of the eastern coast of Madagascar, although it has been recorded as far as 100 km (62 mi) inland. Uniquely in the genus Ptychochromis, this species also occurs in brackish water. It reaches 21.3 cm (8.4 in) in standard length. It shares a large part of its range with a cichlid from another genus, Paretroplus polyactis.