The siege of Budapest or battle of Budapest was the 50-day-long encirclement by Soviet and Romanian forces of the Hungarian capital of Budapest, near the end of World War II. Part of the broader Budapest Offensive, the siege began when Budapest, defended by Hungarian and German troops, was encircled on 26 December 1944 by the Red Army and the Romanian Army. During the siege, about 38,000 civilians died through starvation, military action, and mass executions of Jews by the far-right Hungarian nationalist Arrow Cross Party. The city unconditionally surrendered on 13 February 1945. It was a strategic victory for the Allies in their push towards Berlin.

Budapest is the capital and most populous city of Hungary. It is the ninth-largest city in the European Union by population within city limits and it was the largest city on the Danube river; today it is the second largest one. The city has an estimated population of 1,752,286 over a land area of about 525 square kilometres. Budapest, which is both a city and municipality, forms the centre of the Budapest metropolitan area, which has an area of 7,626 square kilometres and a population of 3,303,786. It is a primate city, constituting 33% of the population of Hungary.