The Battle of Shanghai () was the first of the twenty-two major engagements fought between the National Revolutionary Army (NRA) of the Republic of China (ROC) and the Imperial Japanese Army (IJA) of the Empire of Japan at the beginning of the Second Sino-Japanese War. It lasted from August 13, 1937, to November 26, 1937, and was one of the largest and bloodiest battles of the entire war, later described as "Stalingrad on the Yangtze", and even regarded by some historians as the first battle of World War II. After over three months of extensive fighting on land, in the air and at sea, the battle concluded with a victory for Japan. Both sides accused each other of using chemical weapons during the battle, both without evidence.
Since the Japanese invasion of Manchuria in 1931 followed by the Japanese attack of Shanghai in 1932, there had been ongoing armed conflicts between China and Japan without an official declaration of war. These conflicts finally escalated in July 1937, when the Marco Polo Bridge Incident triggered the full advance from Japan. Dogged Chinese resistance at Shanghai was aimed at stalling Japanese advance, giving much needed time for the Chinese government to move vital industries to the interior, while at the same time attempting to bring sympathetic Western powers to China's side. During the fierce three-month battle, Chinese and Japanese troops fought in downtown Shanghai, in the outlying towns, and on the beaches of the Yangtze River and Hangzhou Bay, where the Japanese had made amphibious landings.
Chinese forces were equipped primarily with small-caliber weapons against much greater Japanese air, naval, and armor power. In the end, Shanghai fell, and China lost a significant portion of its best troops, while failing to elicit any international intervention. However, the resistance of Chinese forces over three months of battle shocked the Japanese, who had been indoctrinated with notions of cultural and martial superiority, and largely demoralized the Imperial Japanese Army, who believed they could take Shanghai within days and China within months.