A Cossack host (, kazachye voysko), sometimes translated as Cossack army, was an administrative subdivision of Cossacks in the Russian Empire. Earlier the term viisko (host) referred to Cossack organizations in their historical territories, most notable being the Zaporozhian Host of Ukrainian Cossacks.

Russian Empire

Each Cossack host consisted of a certain territory with Cossack settlements that had to provide military regiments for service in the Imperial Russian Army and for border patrol operations. Usually the hosts were named after the regions of their location. The stanitsa, or village, formed the primary unit of this organization. In the Russian Empire (1721-1917), the Cossacks constituted twelve separate hosts, settled along the frontiers: There was also a small number of the Cossacks in Krasnoyarsk and Irkutsk, who would form the Yenisey Cossack Host and the Irkutsk Cossack Regiment of the Ministry of the Interior in 1917. Cossack hosts on Russian soil were disbanded in 1920, in the course of the Russian Civil War of 1917–1922 in a deliberate process of De-Cossackization to remove their identity. Cossacks who settled abroad continued to preserve the traditions of their hosts of origin (for example: the Triunited Don-Kuban-Terek Cossack Union founded in Istanbul in January 1921).

List of hosts