The Nanking Massacre or Nanjing Massacre, also known as the Rape of Nanking, was a mass murder, and war rape that occurred during the six-week period following the Japanese capture of the city of Nanjing (Nanking), the former capital of the Republic of China, on December 13, 1937 during the Second Sino-Japanese War. During this period hundreds of thousands of Chinese civilians and disarmed soldiers were murdered by soldiers of the Imperial Japanese Army. Widespread rape and looting also occurred. Historians and witnesses have estimated that 250,000 to 300,000 people were killed. Several of the key perpetrators of the atrocities, at the time labelled as war crimes, were later tried and found guilty at the Nanjing War Crimes Tribunal, and were subsequently executed. Another key perpetrator, Prince Asaka, a member of the Imperial Family, escaped prosecution by having earlier been granted immunity by the Allies.

The event remains a contentious political issue, as various aspects of it have been disputed by some historical revisionists and Japanese nationalists, who have claimed that the massacre has been either exaggerated or wholly fabricated for propaganda purposes. As a result of the nationalist efforts to deny or rationalize the war crimes, the controversy surrounding the massacre remains a stumbling block in Sino-Japanese relations, as well as Japanese relations with other Asia-Pacific nations such as South Korea and the Philippines.