The Shāndōng Peninsula () also known as the Jiāodōng Peninsula (胶东半岛; 膠東半島) is a peninsula in the Shāndōngprovince of northeastern China. It marks the southern limit of the Bóhăi Sea.
The Shandong peninsula formed part of the German concessions in China. After World War I, it was expected that Shandong would be returned to China but instead was signed over to Japan on 30th April, 1919 after it emerged that the Chinese Premier Duan Qirui had signed away Shandong to Japan in return for a loan.
During World War One, Japan had captured the city of Qingdao on the peninsula, which was then held by Germany; Japan had declared war on Germany to satisfy the Anglo-Japanese Alliance.