The Marco Polo Bridge incident, also known as the Lugou Bridge incident or the July 7 incident, was a battle during July 1937 in the district of Beijing between the 29th Army of the National Revolutionary Army of the Republic of China and the Imperial Japanese Army.

Since the Japanese invasion of Manchuria in 1931, there had been many small incidents along the rail line connecting Beijing with the port of Tianjin, but all had subsided. On the night of 7 July 1937, Japanese garrison troops at Lukouchiao held an unusual maneuver; and, alleging that a Japanese soldier was missing, demanded entry into the City of Wanping to conduct a search. Fighting broke out while the Japanese complaint was still under negotiation. However, the missing Japanese soldier had already returned to his lines. The Marco Polo Bridge incident is generally regarded as the start of the Second Sino-Japanese War.