The Battle of Shanghai, known in Chinese as Battle of Songhu, was the first of the twenty-two major engagements fought between the National Revolutionary Army of the Republic of China and the Imperial Japanese Army of the Empire of Japan during the Second Sino-Japanese War. It was one of the largest and bloodiest battles of the entire war.

Since 1931, China and Japan had been embroiled in incessant, smaller conflicts, often known as "incidents," that saw China lose territories piece by piece. The term "incident" was used by the Japanese Imperial High Command to play down the Japanese invasions of China. Although Japan had not formally declared war on China, by August 1937, following the Marco Polo Bridge Incident of July 7 and the ensuing Japanese invasion of North China, a de facto state of war existed between China and Japan.

Dogged Chinese resistance at Shanghai was aimed at stalling the rapid 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 Jiangsu coast, where the Japanese had made amphibious landings.

The Chinese soldiers had to rely primarily on small-caliber weapons in their defense of Shanghai, against an overwhelming onslaught of air, naval, and armored striking power from Japan. In the end, Shanghai fell, and China lost a significant portion of its best troops, while also failing to elicit any international intervention. The resistance of Chinese forces, however, came as a massive shock to the Japanese invaders, who had been indoctrinated with notions of cultural and martial superiority, and dramatically demoralized the Japanese army.

The battle can be divided into three stages, and eventually involved nearly one million troops. The first stage lasted from August 13 to August 22, during which the Chinese army attempted to eradicate Japanese troop presence in downtown Shanghai. The second stage lasted from August 23 to October 26, during which the Japanese launched amphibious landings at Jiangsu coast and the two armies fought a Stalingrad-type house-to-house battle, with the Japanese attempting to gain control of the city and the surrounding regions. The last stage, ranging from October 27 to the end of November, involved the retreat of the Chinese army in the face of Japanese flanking maneuvers, and the ensuing combat on the road to China's capital, Nanjing.