The Zaporozhian Cossacks or Zaporizhian Cossacks, also known as the Zaporozhian Cossack Army or the Zaporozhian Host (Ukrainian: Військо Запорозьке, romanized: Viisko Zaporozke), were Cossacks who lived beyond (that is, downstream from) the Dnieper Rapids. They were predominantly Ruthenians, but also included other ethnic groups (most notably their legendary Kosh Otaman Ivan Sirko was of Moldavian origin). Scientific studies conducted on the Zaporozhian Cossack genetics show that their Y-chromosomal genetic makeup forms the southern fragment of East Slavic population, with minimal levels to absence of Caucasian and Asian component in their paternal gene pool. Along with Registered Cossacks and Sloboda Cossacks, Zaporozhian Cossacks played an important role in the history of Ukraine and the ethnogenesis of Ukrainians.
The Zaporozhian Sich grew rapidly in the 15th century from serfs fleeing the more controlled parts of the Polish–Lithuanian Commonwealth. The least controlled region, that was located between the Dniester and mid-Volga was first known from the 15th century as the Wild Fields, which was subject to colonization by the Zaporozhian Cossacks. Zaporozhian Host became established as a well-respected political entity with a parliamentary system of government. During the course of the 16th, 17th and well into the 18th century, the Zaporozhian Cossacks were a strong political and military force that challenged the authority of the Polish–Lithuanian Commonwealth, the Tsardom of Russia, and the Crimean Khanate.
