a river in Voroshilovgrad and Donetsk Oblasts, Ukrainian SSR, and in Rostov Oblast, RSFSR. Length, 258 km; basin area, 6,680 sq km.

The Mius finds its source on the Donets Ridge and falls into the Mius Estuary of the Sea of Azov. It is fed primarily by snow and rain. Average water discharge at a point 65 km from the mouth is 12.1 cu m per sec. Low water is from May through January; the river freezes in December and thaws in February or March. The Mius is widely used as an industrial water supply. Eight small reservoirs and many ponds have been dug in the basin.

During the Great Patriotic War of 1941–45, fascist German troops established a highly fortified defensive line on the Mius, which they designated the Mius Front and which they held from December 1941 until July 1942 and from February until August, 1943. In August 1943, during the Donbas Offensive Operation, Soviet troops of the Southern Front broke through this powerful line in the area of Kuibyshevo.