Kiev was the center of Vladimir I’s Viking-founded state, Kievan Rus’.
The city stood on the Dnieper River, a crucial route linking Scandinavia with the Black Sea and Constantinople. Scandinavian warriors and traders known as Varangians became part of the ruling elite, while the population and administration were largely East Slavic. The state that developed around Kiev became one of medieval Eastern Europe’s most important political and cultural powers.
Vladimir I ruled from 980 to 1015. In 988, he adopted Christianity and initiated the Christianization of Kievan Rus’, a decision that profoundly shaped the religious history of Ukraine, Belarus, and Russia. Kiev’s location helped it control trade, diplomacy, and military movement along the river system.
Modern English generally uses Kyiv, reflecting the Ukrainian transliteration, while Kiev is the older and still historically common English spelling. The question’s “Viking state” wording refers to the Varangian origins of the ruling dynasty, not to a kingdom composed exclusively of Scandinavians.