The Ukrainian stickleback (Pungitius platygaster) also known as the Caspian ninespine stickleback, southern ninespine stickleback, and Aral ninespine stickleback, is a species of fish in the family Gasterosteidae. It is found in Afghanistan, Bulgaria, Iran, Kazakhstan, Moldova, Romania, Russia, Serbia, Montenegro, and Ukraine (Black Sea, Sea of Azov, Aral Sea and Caspian Sea basins).

Ukrainian stickleback
Ukrainian stickleback from the Dniester Estuary, Ukraine
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Scorpaeniformes
Family:	Gasterosteidae
Genus:	Pungitius
Species:	P. platygaster
Binomial name
Pungitius platygaster (Kessler, 1859)
Synonyms
Gasterosteus platygaster Kessler, 1859 Gasterosteus platygaster aralensis Kessler, 1877 Gasterosteus platygaster caucasicus Kessler, 1877 Gasterosteus platygaster danubica Steindachner, 1899 Gasterosteus platygaster kessleri Yakovlev, 1870 Gasterosteus platygaster niger Yakovlev, 1870 Gasterosteus pungitius niger Yakovlev, 1870 Pungitius platygaster aralensis (Kessler, 1877) Pygosteus platygaster nuda Berg, 1905

A combination of two characters: lack of caudal peduncle keel, presence of large lateral scutes. It is similar to P. hellenicus with the following differences. Body darker than P. hellenicus (juvenile specimens from Iran show the same color as P. hellenicus). All the bones well ossified, cranial bones and pelvic bones highly sculptured. Pelvic girdle present with one spine and one small soft ray on each side. Dorsal spines 8–11, inclined alternatively to left and right. Last spine slightly longer than the others, which are relatively uniform. Dorsal soft rays 6–10; anal soft rays 6–9; gill rakers 9–11; bony scutes 29–32 with 7-12 large lateral scutes; total vertebrae 29–31; precaudal vertebrae usually 13. Caudal fin truncated.