Kozmodemyansk is a town (since 1781) in Russia, administrative center of Gornomariysky District of Mari El.

The town is located on the high right bank of the Volga (the Cheboksary storage), in 104 km southwest of Yoshkar-Ola. Ferry service connects the town with the left-bank part of the Republic. It is the main cultural center of the Hill Mari.

The town was founded in 1583. Since 1708 it was in the Kazan Governorate, since 1719 — in the Sviyazhsk province, since 1781 it is a district town of the Kazan region. Since the second half of the 19th century the town was the second lumber-trade center in Russia (after Arkhangelsk). According to legend, Kozmodemyansk is founded by the first Tsar Ivan the Terrible, after he won a victory over the Kazan khanate with Hill Mari hero Akpars, during he came back to Moscow on the river, he saw a high hill and ordered the build a settlement.

At present the most stable town enterprises are the close stock company «Potentsial», public stock company «Maria», public stock company «Kopir», public stock company «Proizvodstvennik» and others.

Radio manufacturing plant «Potentsial» belongs to Wessen Group. (Besides the company has 7 sales offices in Russia.) Wessen is one of the leaders among Russian manufacturers of wiring products. Every third socket or switch sold in Russia is production of the plant. Since June 17, 2008 Wessen Group belongs to the French company Schneider Electric.

The town is in constant danger of underflooding by the Cheboksary storage. In the town there is the Kozmodemyansk museum complex:

In the town there is the Hill Mari drama theatre.

The composer Andrei Yakovlevich Eshpai was born in Kozmodemyansk (1925).

In the town the so-called Streletsky Tower is a chapel built in 1697. In Kozmodemyansk the humorous Festival “Benderiada” is being hold since 1995, named after the hero of novels by Ilf and Petrov Ostap Bender. Some literary critics consider that a prototype for the described in the novel “The Twelve Chairs” the town Vasyuki was the town Kozmodemyansk, but inhabitants of the superposed Vasilsursk dispute this fact.