Kievan Rus'

Kievan Rus' (Old East Slavic: Роусь, romanized: Rusĭ, or роусьскаѧ землѧ, romanized: rusĭskaę zemlę, "Rus' land") or Kyivan Rus', was a loose federation of East Slavic, Baltic and Finnic peoples in Eastern and Northern Europe from the late 9th to the mid-13th century, under the reign of the Rurik dynasty, founded by the Varangian prince Rurik. The modern nations of Belarus, Russia, and Ukraine all claim Kievan Rus' as their cultural ancestors, with Belarus and Russia deriving their names from it. The Rurik dynasty would continue to rule parts of Rus' until the 16th century with the Tsardom of Russia. At its greatest extent, in the mid-11th century, it stretched from the White Sea in the north to the Black Sea in the south and from the headwaters of the Vistula in the west to the Taman Peninsula in the east, uniting the majority of East Slavic tribes.

During its existence, Kievan Rus' was known as the "land of the Rus" (Old East Slavic: ро́усьскаѧ землѧ, from the ethnonym Ро́усь; Greek: Ῥῶς; Arabic: الروس ar-Rūs), in Greek as Ῥωσία, in Old French as Russie, Rossie, in Latin as Rusia or Russia (with local German spelling variants Ruscia and Ruzzia), and from the 12th century also as Ruthenia or Rutenia. Various etymologies have been proposed, including Ruotsi, the Finnish designation for Sweden or Ros, a tribe from the middle Dnieper valley region.

During its existence, Kievan Rus' was known as the "land of the Rus" (Old East Slavic: ро́усьскаѧ землѧ, from the ethnonym Ро́усь; Greek: Ῥῶς; Arabic: الروس ar-Rūs), in Greek as Ῥωσία, in Old French as Russie, Rossie, in Latin as Rusia or Russia (with local German spelling variants Ruscia and Ruzzia), and from the 12th century also as Ruthenia or Rutenia. Various etymologies have been proposed, including Ruotsi, the Finnish designation for Sweden or Ros, a tribe from the middle Dnieper valley region.

The state began to decline during the late 11th century and the 12th century, disintegrating into various rival regional powers. It was further weakened by economic factors, such as the collapse of Rus' commercial ties to the Byzantine Empire due to the decline of Constantinople and the accompanying diminution of trade routes through its territory. The state finally fell to the Mongol invasion of the 1240s.

According to Rus' Primary Chronicle, the first ruler to start uniting East Slavic lands into what has become known as Kievan Rus' was Prince Oleg (879–912). He extended his control from Novgorod south along the Dnieper river valley to protect trade from Khazar incursions from the east, and moved his capital to the more strategic Kiev. Sviatoslav I (died 972) achieved the first major expansion of Kievan Rus' territorial control, fighting a war of conquest against the Khazars. Vladimir the Great (980–1015) introduced Christianity with his own baptism and, by decree, extended it to all inhabitants of Kiev and beyond. Kievan Rus' reached its greatest extent under Yaroslav the Wise (1019–1054); his sons assembled and issued its first written legal code, the Russkaya Pravda ("Rus' Justice"), shortly after his death.

Kievan Rus' (Old East Slavic: Роусь, romanized: Rusĭ, or роусьскаѧ землѧ, romanized: rusĭskaę zemlę, "Rus' land") or Kyivan Rus', was a loose federation of East Slavic, Baltic and Finnic peoples in Eastern and Northern Europe from the late 9th to the mid-13th century, under the reign of the Rurik dynasty, founded by the Varangian prince Rurik. The modern nations of Belarus, Russia, and Ukraine all claim Kievan Rus' as their cultural ancestors, with Belarus and Russia deriving their names from it. The Rurik dynasty would continue to rule parts of Rus' until the 16th century with the Tsardom of Russia. At its greatest extent, in the mid-11th century, it stretched from the White Sea in the north to the Black Sea in the south and from the headwaters of the Vistula in the west to the Taman Peninsula in the east, uniting the majority of East Slavic tribes.