Kievan Rus'

State · 882–1240 CE · at its largest around 1034 CE

A federation of East Slavic principalities ruled by the Rurikid dynasty from Kiev. Vladimir the Great adopted Christianity in 988; the Mongols sacked Kiev in 1240.

On its lands while it lasted

Varangians to the Greeks (c. 800–1100 CE): Scandinavian traders and warriors travelled from the Baltic up the Neva and Volkhov past Novgorod, portaged to the Dnieper and sailed down past Kiev to the Black Sea and Constantinople.
Founding of Kievan Rus' (882 CE): Oleg of Novgorod took Kyiv and made it his capital, creating the state of Kievan Rus', which united East Slavic lands under the Rurik dynasty.
Pskov (903 CE): Capital of Pskov Republic (1348–1510).
Vitebsk (974 CE): Capital of Principality of Vitebsk (1111–1187).
Christianization of Kievan Rus' (988 CE): Vladimir the Great adopted Orthodox Christianity from Byzantium and had the people of Kyiv baptised in the Dnieper.
Vladimir (990 CE): Capital of Principality of Rostov-Suzdal (1125–1240), Principality of Vladimir-Suzdal (1294–1389).
Suzdal (1024 CE): Capital of Principality of Rostov-Suzdal (1125–1240), Principality of Vladimir-Suzdal (1294–1389).
Chernihiv (c. 1056 CE): Capital of Principality of Chernigov (1056–1240).
Volodymyr (c. 1056 CE): Capital of Principality of Volhynia (1056–1201), Halych-Volhynia occupation (1199–1240), Principality of Galicia-Volhynia (1202–1240), and 1 more.
Pereiaslav (c. 1056 CE): Capital of Principality of Pereyaslavl (1056–1239).
Ryazan (1095 CE): Capital of Principality of Ryazan (1097–1240), Ryazan (1453–1520).
Minsk (c. 1111 CE): Capital of Principality of Minsk (1111–1313), Republic of Belarus (1992–today).
Rostov Veliky (c. 1125 CE): Capital of Principality of Rostov-Suzdal (1125–1240), Principality of Vladimir-Suzdal (1294–1389).
Sandomierz (c. 1139 CE): Capital of Duchy of Sandomierz (1139–1304).
Mongol invasion of Kievan Rus' (1237–1242 CE): Mongol armies under Batu Khan destroyed Ryazan, Vladimir and Kyiv, subjecting the Rus' principalities to Mongol overlordship for over two centuries.