The Battle of Poltava (8 July 1709) was the decisive and largest battle of the Great Northern War. A Russian army under the command of Tsar Peter I defeated a Swedish army, under the command of Carl Gustaf Rehnskild. The battle put an end to the status of the Swedish Empire as a European great power, as well as its eastbound expansion, and marked the beginning of Russian hegemony in Northern Europe.

During the course of six years in the initial stages of the war, King Charles XII and the Swedish Empire had defeated almost all participants in the anti-Swedish coalition, which initially consisted of the Polish-Lithuanian Commonwealth, Denmark-Norway and the Tsardom of Russia. The latter under Tsar Peter I's rule was the only one still undefeated. Charles XII therefore chose to invade Russia in the autumn of 1707 and march towards Moscow with a large Swedish army. However, the campaign was complicated by harsh weather conditions and by the Russians applying scorched earth tactics:704 and surprise attacks, which forced Charles XII to interrupt his march on Moscow and instead march south to establish winter quarters in former Rus (modern day Ukraine) with the help of Ivan Mazepa, hetman of the Zaporizhian Host.

After the extremely harsh Great Frost of 1708-1709, the weakened Swedish army resumed operations in the spring of 1709 and began a siege of the fortress of Poltava, an important trading center and military depot on the Vorskla. Meanwhile, a numerically superior Russian army of 75,000-80,000 men commanded by Peter, advanced to Poltava in order to relieve the siege. The two armies clashed, and ended with the Swedes being defeated and fleeing the battlefield. Charles and Mazepa retreated with 1,500 men south to the river Dnieper, which they crossed, thus managing to escape the Russians and established themselves in the Ottoman Empire.:710 The rest of the army was forced to surrender to the Russians at the village of Perevolochna on July 11, 1709.The Battle of Poltava, as well as the subsequent capitulation, ended in a decisive victory for Peter I and became the greatest military catastrophe in Swedish history. It marked a turning point in the continuation of the war in favour of the anti-Swedish coalition, which as a result of the battle was revived and with renewed vigor attacked the weakened Swedish Empire on several fronts. The battle thus marked the end of Sweden's time as the dominant power in Northern Europe, a position which after the war was taken over by the Russian Empire. The battle is therefore of crucial importance in the history of Sweden as well as Russia and Ukraine.

Peter the Great (Russian: Пётр Вели́кий, tr. Pyotr Velíkiy, IPA: [ˈpʲɵtr vʲɪˈlʲikʲɪj]), Peter I or Pyotr Alekséyevich (Russian: Пётр Алексе́евич, IPA: [ˈpʲɵtr ɐlʲɪˈksʲejɪvʲɪtɕ]; 9 June [O.S. 30 May] 1672 – 8 February [O.S. 28 January] 1725) was a monarch of the Tsardom of Russia and later the Russian Empire from 7 May [O.S. 27 April] 1682 until his death in 1725, jointly ruling before 1696 with his elder half-brother, Ivan V. Under his reign, Russia was modernised and grew into a European power.

Through a number of successful wars, he captured ports at Azov and the Baltic Sea, laying the groundwork for the Imperial Russian Navy, ending uncontested Swedish supremacy in the Baltic and beginning the Tsardom's expansion into a much larger empire that became a major European power. He led a cultural revolution that replaced some of the traditionalist and medieval social and political systems with ones that were modern, scientific, Westernised and based on the Enlightenment. Peter's reforms had a lasting impact on Russia, and many institutions of the Russian government trace their origins to his reign. He adopted the title of Emperor in place of the old title of Tsar in 1721, and founded and developed the city of Saint Petersburg, which remained the capital of Russia until 1917.

However, the formation of local elites domestically was not his main priority, and the first Russian university—Saint Petersburg State University—was founded only a year before his death, in 1724. The second one, Moscow State University, was founded 30 years after his death, during the reign of his daughter Elizabeth.