The Ostiaks call themselves As-yakh (people of the Ob), and it is supposed that their present designation is a corruption of this name. By language they belong (Castrén, Reiseberichte, Reisebr-iefe; AhIqvist, Ofvers. af Finska Vet.-Soc. Förh. xxi.) to the Ugrian branch of the eastern Finnish stem. All the Ostiaks speak the same language, mixed to some extent with foreign elements; but three or four leading dialects can be distinguished.
The Ostiaks are middle-sized, or of low stature, mostly meagre, and not ill made, however clumsy their appearance in winter in their thick fur-clothes. The extremities are fine, and the feet are usually small. The skull is brachycephalic, mostly of moderate size and height. The hair is dark and soft for the most part, fair and reddish individuals being rare; the eyes are dark, generally narrow; the nose is flat and broad; the mouth is large and with thick lips; the beard is scanty. The Mongolian type is more strongly pronounced in the women than in the men. On the whole, the Ostiaks are not a pure race; the purest type is found among the fishers on the Ob, the reindeer-breeders of the tundra being largely intermixed with Samoyedes. Investigators describe them as kind, gentle and honest; rioting is almost unknown among them, as also theft, this last occurring only in the vicinity of Russian settlements, and the only penalty enforced being the restitution twofold of the property stolen.
They are very skilful in the arts they practice, especially in carving wood and bone, tanning (with egg-yolk and brains), preparation of implements from birch-bark, &c. Some of their carved or decorated bark implements (like those figured in Middendorif's Sibirische Reise, iv. 2) show considerable artistic skill.
Their folklore, like that of other Finnish stems, is imbued with a feeling of natural poetry, and reflects also the sadness, or even the despair, which has been noticed among them. Christianity has made some progress among them and St Nicholas is a popular saint, but their ancient pagan observances are still retained.
For the language see Ahlquist, Über die Sprache der Nord-Ostyaken (1880) and for customs, religion, &c., the Journal de la Société Finno-Ougrienne, particularly papers by Sirelius and Karjalainen, and the papers by Munkhcsi, Gennep, Fuchs and others in the Revue orientale pour les etudes Ouralo-Altafques; Patkanov, Die Irtyscli-Ostiaken und ihre Volkspoesie (Petersburg, 1900); Patkanov, Irtirsch-Ostjaken und ihre Volkspoesie (1897-1900); Papay, Sammiung ostjizkischer Volksdichtungen (1906).