Sviatoslav or Svyatoslav I Igorevich was Prince of Kiev from 945 until his death in 972. He is known for his persistent campaigns in the east and south, which precipitated the collapse of two great powers in Eastern Europe, Khazaria and the First Bulgarian Empire. He conquered numerous East Slavic tribes, defeated the Alans and attacked the Volga Bulgars, and at times was allied with the Pechenegs and Magyars (Hungarians).
Sviatoslav I by Eugene Lanceray (1886)
Sviatoslav's mother, Olga, with her escort in Constantinople, a miniature from the late 11th century chronicle of John Skylitzes.
Sviatoslav's Council of War by Boris Chorikov
Sviatoslav invading Bulgaria, Manasses Chronicle
The Grand Prince of Kiev was the title of the monarch of Kievan Rus', residing in Kiev from the 10th to 13th centuries. In the 13th century, Kiev became an appanage principality first of the grand prince of Vladimir and the Mongol Golden Horde governors, and later was taken over by the Grand Duchy of Lithuania.
Regnal list in the opening lines of the Khlebnikov Codex: 'In Kiev, the first to begin reigning together were Dinar and Askold, after them came Olga, after Olga Igor...'