The Supreme Commander for the Allied Powers was the title held by General Douglas MacArthur during the United States-led Allied occupation of Japan following World War II. It issued SCAP Directives to the Japanese government, aiming to suppress its "militaristic nationalism". The position was created at the start of the occupation of Japan on August 14, 1945. It was originally styled the Supreme Commander of the Allied Powers.

Japan was occupied and administered by the Allies of World War II from the surrender of the Empire of Japan on September 2, 1945, at the war's end until the Treaty of San Francisco took effect on April 28, 1952. The occupation, led by the American military with support from the British Commonwealth and under the supervision of the Far Eastern Commission, involved a total of nearly one million Allied soldiers. The occupation was overseen by the US General Douglas MacArthur, who was appointed Supreme Commander for the Allied Powers by the US President Harry S. Truman; MacArthur was succeeded as supreme commander by General Matthew Ridgway in 1951. Unlike in the occupations of Germany and Austria, the Soviet Union had little to no influence in Japan, declining to participate because it did not want to place Soviet troops under MacArthur's direct command. And unlike Germany, the Japanese government still remained in place throughout the occupation.