Kostek (Russian: Костек; Kumyk: Кёстек, Köstek) is a village (selo) in the Khasavyurt District of the Republic of Dagestan in Russia. As of the 2010 Census, its population was 4,551. It is the administrative center of the rural settlement of Kostekskogo.

Kostek is situated to north-east of the city of Khasavyurt. Nearby settlements include Aknada and Yazykovka (Akaro) to the northeast, Kurush to the north-west, Chontaul to the south, and Novo-Kostek to the south-east.

Kostek — settlement in Terek oblast of Khasavyurtovsky District. Population – 4588. A synagogue, 8 mosks, 1 school, 1 drinking establishment, 27 commercial and 16 industrial establishments. Residents — Kumyks.

— Brockhaus and Efron Encyclopedic Dictionary.

Kostek settlement is founded approximately in the 60s-70s of the 17th century by an Enderi prince Alish Khamzin. By the beginning of the 18th century, Kostek developed into a large settlement of Kostek Principality.

At midday I reached a Tatar-Kumyk village Kostek. It is situated near river Koysuv… The village stands on an open plain with approximately 200 houses which are made according to local traditions of clayed twisted rods. The village belongs to prince Khamurza from the Shamkhala family. Local residents are Kumyk Tatars and a few Armenians. Main crafts – agriculture and fishing. Here are good wheat and even bigger rice fields in the lowlands of river Koysuv… Small amounts of cotton are also produced here for sale. Silk is produced only for local use.

— J. Güldenstädt Reisen durch Rußland und im Caucasischen Gebürge. 1787-1791

By the middle of the 19th century, the settlement stopped being the centre of Kostek Principality, but became a significant local trade centre where fairs were organized every week. In 1876 a Russian school was opened, where children of rich Kumyk families were taught. Having finished this school they entered military academies and became officers of Russian Imperial Army.