Petro Konashevych-Sahaidachny was a political and civic leader, who was a Hetman of Ukrainian Cossacks from 1616 to 1622. During his tenure, he transformed Zaporozhian Cossacks from irregular military troops into a regular army and improved relations between the Cossacks, the Orthodox clergy and peasants of Ukraine, which would later contribute to the establishment of a modern Ukrainian national consciousness. A military leader of the Polish–Lithuanian Commonwealth both on land and sea, Sahaidachny is best known for the significant role his troops played in the Battle of Khotyn against the Ottoman Empire in 1621, as well as the Polish Prince Władysław IV Vasa's attempt to usurp the Russian throne in 1618.

The Zaporozhian Cossacks, Zaporozhian Cossack Army, Zaporozhian Host, or simply Zaporozhians were Cossacks who lived beyond the Dnieper Rapids. Along with Registered Cossacks and Sloboda Cossacks, Zaporozhian Cossacks played an important role in the history of Ukraine and the ethnogenesis of Ukrainians.