The Cossacks are a predominantly East Slavic Orthodox Christian people originating in the Pontic–Caspian steppe of eastern Ukraine and southern Russia. Historically, they were a semi-nomadic and semi-militarized people, who, while under the nominal suzerainty of various Eastern European states at the time, were allowed a great degree of self-governance in exchange for military service. Although numerous linguistic and religious groups came together to form the Cossacks, most of them coalesced and became East Slavic-speaking Orthodox Christians.

The Pontic–Caspian Steppe is a steppe extending across Eastern Europe to Central Asia, formed by the Caspian and Pontic steppes. It stretches from the northern shores of the Black Sea to the northern area around the Caspian Sea, where it ends at the Ural-Caspian narrowing, which joins it with the Kazakh Steppe in Central Asia, making it a part of the larger Eurasian Steppe. Geopolitically, the Pontic-Caspian Steppe extends from northeastern Bulgaria and southeastern Romania through Moldova and eastern Ukraine, through the North Caucasus of southern Russia, and into the Lower Volga region where it straddles the border of southern Russia and western Kazakhstan. Biogeographically, it is a part of the Palearctic realm, and of the temperate grasslands, savannas, and shrublands biome.