Charaxes (Polyura) cognatus, the Sulawesi blue nawab, is a butterfly in the family Nymphalidae.

[2] Polyura cognatus is a large butterfly with forewings with a concave outer edge and hindwings with two tails each.

(135 a) replaces schreiber in Celebes and agrees with it in the rare chromatic symphony of black, blue and white.

Median area of the hindwings horter but more extensively encircled by a blue tinge than in the Javanese race of E. schreiber.

Under surface characterized by a pronounced net of black stripes surrounding and defining two silvery white spots of the cell of the forewing and the median band of the hindwing.cognatus is rare in all the parts of the island, but seems to occur the most numerously in August in the north, as for instance near Palu, as well as in the south of Celebes.