Kozmodemyansk is a city in Russia, the administrative center of the Gornomariysky Region of Mary El Republic.

It has a population of 22.7 thousand people (as of 2010). The city is located on the high right bank of Volga River (Cheboksary Reservoir), 104 km South to the west of Yoshkar-Ola. A ferry connects the city to the left-bank part of the republic. It is the main cultural center of the Mari people.

The city was founded in 1583. From 1708 it was a part of the Kazan Province, from 1719 — a part of the Sviyazhsky Province, from 1781 — the chief town of the Kazan Region.

From the second half of the 19th century the city ranked second in Russia (after Arkhangelsk) as the wood trading center.

Kozmodemyansk has s number of museums:

A.V. Grigoriev's Art and History Museum with canvasses by Kustodiyev, Vrubel, Shishkin, Golovin, and Malyavin; the open-air Ethnographic Museum with an exposition that demonstrates the way of life and culture of the Mari people; Museum of Merchant Household with interiors, furniture, and household items of a merchant’s house; and Ostap Bender Museum with installations and household items in this or that way concerning the popular novels “12 chairs” and “The Gold Calf” by Ilf and Petrov.

The comic festival Benderiada named after the famous character of Ilf and Petrov’s novels Ostap Bender has been annually held in Kozmodemyansk since 1995.

The Gornomariysky Drama Theater works in the city.

The so-called Streletsky Tower — a chapel constructed in 1697 - has remained in the city till date.