Don Cossacks or Donians, are Cossacks who settled along the middle and lower Don. Historically, they lived within the former Don Cossack Host, which was either an independent or an autonomous democratic republic in present-day Southern Russia and parts of the Donbas region of Ukraine, from the end of the 16th century until 1918. As of 1992, by presidential decree of the Russian Federation, Cossacks can be enrolled on a special register. A number of Cossack communities have been reconstituted to further Cossack cultural traditions, including those of the Don Cossack Host. Don Cossacks have had a rich military tradition - they played an important part in the historical development of the Russian Empire and participated in most of its major wars.

Yermak Timofeyevich was a Cossack ataman and is today a hero in Russian folklore and myths. During the reign of the Russian tsar Ivan the Terrible, Yermak started the Russian conquest of Siberia.