The Soviet invasion of Manchuria, formally known as the Manchurian Strategic Offensive Operation or simply the Manchurian Operation, began on 9 August 1945 with the Soviet invasion of the Japanese puppet state of Manchukuo. It was the largest campaign of the 1945 Soviet–Japanese War, which resumed hostilities between the Union of Soviet Socialist Republics and the Empire of Japan after almost six years of peace. Since 1983, the operation has sometimes been called Operation August Storm after U.S. Army historian David Glantz used this title for a paper on the subject.

Manchukuo was a puppet state of the Empire of Japan in Northeast China that existed from 1932 until its dissolution in 1945. It was ostensibly founded as a republic, its territory consisting of the lands seized in the Japanese invasion of Manchuria; it was later declared to be a constitutional monarchy in 1934, though very little changed in the actual functioning of government. Manchukuo received limited diplomatic recognition, mostly from states aligned with the Axis powers, with its existence widely seen as illegitimate.