The Novgorod Republic (Old Russian: Новгородскаѧ земьлѧ) was a medieval Russian state controlled from the city of the same name. Over time it became the most powerful Russian principality and eventually evolved into the Grand Duchy of Russland, a founding member of the Lithuanian-Polish-Russian Commonwealth.
Novgorod served as the original capital of the Rus' until 882, when the capital was moved to Kiev by Helgi the Wise. It remained however a political and spiritual centre, and its people and rulers were granted numerous freedoms and privileges by successive Kievan princes. From about 1054, as Kievan central power declined, Novgorod became increasingly independent, culminating in the revolt of 1136 when the Novgorod boyars expelled the Kiev-appointed prince from the city and chose one of their own.
When Kiev was sacked in 1240 by invading Mongols, Novgorod lost its last political ties to the other Russian states. It, along with many other states, was able to preserve its independence by agreeing to pay tribute to the Mongol khan, and was able to take advantage of the power vacuum to expand its territories into smaller neighbours. Before long it came into conflict with Vladimir-Suzdal and Muscovy, and fought several wars against them over the northern Rus lands.