Nematolebias whitei, the Rio pearlfish, is a species of killifish from the family Rivulidae.

It is endemic to Brazil where it is found in the Laguna de Araruama basin, Das Ostras River basin and in coastal plains in the vicinity of the mouth of São João River in Rio de Janeiro State.

[4] Nematolebias whitei is found in small temporary, shallow pools of freshwater on the floodplains of streams and lagoons which have a compact, soft reddish brown muddy substrate and which dry out twice a year.

When these pools dry out all the fish die and the eggs which have been laid in the muddy bottom go through diapause.

[5] The species was described as Cynolebias whitei by George S. Myers in 1942 with the type locality given as a drying out swamp which was 10 or 12 miles (16 or 19 km) north of Cabo Frio in Rio de Janeiro State.