The Kalmius (Ukrainian: Кальміус, Russian: Кальмиус) is a river flowing through Donetsk Oblast, Ukraine.

The Kalmius flows into the Sea of Azov near the Azovstal Iron and Steel Works in Mariupol.

[citation needed] Kalmius is said to be the name of a 16th-century Cossack encampment where the town of Pavlovsk was founded, later renamed Mariupol.

[2] A Donetsk People's Republic unit was named the Kalmius Brigade after the river.

However, the Ukrainian government does not control Kalmiuske, and the new name is not recognized by the pro-Russian occupation authorities.