The siege of Plevna or Pleven, was a major battle of the Russo-Turkish War of 1877–1878, fought by the joint army of the Russian Empire and the Kingdom of Romania against the Ottoman Empire. After the Russian army crossed the Danube at Svishtov, it began advancing towards the centre of modern Bulgaria, with the aim of crossing the Balkan Mountains to Constantinople, avoiding the fortified Turkish fortresses on the Black Sea coast. The Ottoman army led by Osman Pasha, returning from Serbia after a conflict with that country, was massed in the fortified city of Pleven, a city surrounded by numerous redoubts, located at an important road intersection.

After two unsuccessful assaults, in which he lost valuable troops, the commander of the Russian troops on the Balkan front, Grand Duke Nicholas of Russia insisted by telegram on the help of his Romanian ally King Carol I. King Carol I crossed the Danube with the Romanian Army and was placed in command of the Russian-Romanian troops. He decided not to make any more assaults, but to besiege the city, cutting off the food and ammunition supply routes.

At the beginning of the siege, the Russian-Romanian army managed to conquer several redoubts around Pleven, keeping in the long run only the Grivitsa redoubt. The siege, which began in July 1877, did not end until December of the same year, when Osman Pasha was wounded in a failed breakout attempt. Finally, Osman Pasha received the delegation led by General Mihail Cerchez and accepted the conditions of capitulation offered by him. The Turkish general, Osman Pasha, when he capitulated and declared himself a prisoner during the Russo-Turkish War, handed over his sword to the Romanian general Mihail Cerchez, commander of the Romanian troops in Pleven. It was housed in the Museum of the Iron Gates Region, but was stolen in 1992.

The Russian–Romanian victory on 10 December 1877 was decisive for the outcome of the war and the Liberation of Bulgaria. Following the battle, the Russian armies were able to advance and forcefully attack the Shipka Pass, succeeding in defeating the Ottoman defense and opening their way to Constantinople.

In July 1877, the Russian Army, under the command of Grand Duke Nicholas, moved toward the Danube River virtually unopposed, as the Ottomans had no sizable force in the area. The Ottoman high command sent an army under the command of Osman Nuri Pasha to reinforce Nikopol, but the city fell to the Russian vanguard in the Battle of Nikopol (16 July 1877) before Osman reached it. He settled on Plevna, a town among vineyards in a deep rocky valley some twenty miles to the south of Nikopol, as a defensive position. The Ottomans quickly created a strong fortress, raising earthworks with redoubts, digging trenches, and quarrying out gun emplacements. From Plevna Osman's army controlled the main strategic routes to the Balkan Mountains. As the Turks hurried to complete their defenses, Russian forces began to arrive.

General Yuri Schilder-Schuldner, commanding the Russian 5th Division, IX Corps, received orders to occupy Plevna. Schilder-Schuldner arrived outside the town on 19 July and began bombarding the Ottoman defenses. The next day his troops attacked and succeeded in driving Ottoman forces from some of the outer defenses; however, Osman Pasha brought up reinforcements and launched a series of counterattacks, which drove the Russians from the captured trenches, inflicting 3,000 casualties at a cost of 2,000 of his own men.

Osman Pasha strengthened his defences and built more redoubts, his force growing to 22,000 men and 58 guns, while the Russians obtained reinforcements from the army of Prince Carol of Romania (later king Carol I of Romania), who received the command of the joint besieging force. General Nikolai Kridener also arrived with the Russian IX Corps. The overall number of Russian troops increased to 35,000 and 176 guns. On 31 July Russian headquarters ordered Kridener to assault the town, attacking from three sides, with every expectation of a Russo-Romanian triumph. General Alexey Schakhovskoy's cavalry attacked the eastern redoubts, while an infantry division under General Mikhail Skobelev assailed the Grivitsa redoubt to the north. Schakhovskoy managed to take two redoubts, but by the end of the day the Ottoman forces succeeded in repulsing all the attacks and retaking lost ground. Russian losses amounted to 7,300, and the Ottomans' to more than 2,000.^{[citation needed]}

The third battle of Plevna is also called the "Great Assault". After repulsing the Russian attacks, Osman failed to press his advantage and possibly drive off the besiegers; he did, however, make a cavalry sortie on 31 August that cost the Russian 1,300 men, and the Ottomans 1,000. The Russians continued to send reinforcements to Plevna, and their army, now personally led by the Grand Duke swelled to 100,000 men. On 3 September Skobelev reduced the Turkish garrison guarding the Ottoman supply lines at Lovech before Osman could move out to relieve it. The Ottoman army organized the survivors of Lovech into 3 battalions for the Plevna defenses. Osman also received a reinforcement of 13 battalions, bringing his total strength to 30,000 men-the highest it would reach during the siege.