The siege of Sevastopol, also known as the defence of Sevastopol or the Battle of Sevastopol, was a military engagement that took place on the Eastern Front of the Second World War. The campaign was fought by the Axis powers of Germany and Romania against the Soviet Union for control of Sevastopol, a port in Crimea on the Black Sea. On 22 June 1941, the Axis invaded the Soviet Union during Operation Barbarossa, with Axis land forces reaching the Crimean peninsula in the autumn of 1941 and overrunning most of the area. The only objective not in Axis hands was Sevastopol. Several attempts were made to secure the city in October and November 1941. A major attack was planned for late November, but heavy rains delayed it until 17 December 1941. Under the command of Erich von Manstein, Axis forces were unable to capture Sevastopol during this first operation. Soviet forces launched an amphibious landing on the Crimean peninsula at Kerch in December 1941 to relieve the siege and force the Axis to divert forces to defend their gains. The operation saved Sevastopol for the time being, but the bridgehead in eastern Crimea was eliminated in May 1942.

Sevastopol, sometimes written Sebastopol, is the largest city in Crimea and a major port on the Black Sea. Due to its strategic location and the navigability of the city's harbours, Sevastopol has been an important port and naval base throughout its history. Since the city's founding in 1783 it has been a major base for Russia's Black Sea Fleet. During the Cold War of the 20th century, it was a closed city. The total administrative area is 864 square kilometres (334 sq mi) and includes a significant amount of rural land. The urban population, largely concentrated around Sevastopol Bay, is 479,394, and the total population is 547,820.