Sviatoslav I, Prince of Kiev (c. 945 – 972) was the warrior Varangian prince of Kiev, who carved out for himself the largest state in Europe and finally moved his capital to Pereyaslavets in Bulgaria in 969.

We have no information about Svyatoslav's minority and youth, which he spent reigning in Novgorod. His mother, Saint Olga, ruled as Kievan regent until his majority (c.963). Sviatoslav was notorious as a stubborn pagan who rejected the Christianity, which had been embraced by his mother ca 945 or (more likely) in 957.

Svyatoslav's life was spent with his druzhina in permanent warfare against neighbouring states. During his reign, he created an empire that stretched from the Volga to the Danube. His greatest success was the conquest of Khazaria, which for centuries had been one of the strongest states of Eastern Europe. By 965 he also defeated the Volga Bulgars, thus bringing under Kievan control the entire area of the Volga River. Then, as an ally of the Byzantine Empire, which was at war with the Bulgarians, Sviatoslav decisively defeated the Bulgarians of the Danube (968), thereby paving the way for victories of Basil the Bulgar-Slayer.

In moving his capital to Bulgaria, Svyatoslav intended to make it the center of his extensive empire. He was forced to give up the Balkan lands (971), however, in a war with the Byzantine Emperor John I. His unorthodox appearance was noted by the Greeks, who described him as having shaved one side of his head, and having a single large gold earring. During his return from the abysmal Byzantine campaign, Sviatoslav was ambushed and killed by the Pechenegs (972). According to the Primary Chronicle, his skull was made into a chalice by the Pecheneg khan.