The Battle of Jiangnan was a battle between the Qing government's Green Standard Army and the army of the Taiping Heavenly Kingdom during the Taiping Rebellion. The Green Standard Army twice attempted to besiege Nanjing, capital of the Taiping Heavenly Kingdom, but was unable to break through. To break the siege of Nanjing, the Taiping forces maneuvered to divert Qing forces by sacking Hangzhou, before quickly moving back to Nanjing to counter-encircle the Qing siege forces and routing the Green Standard Army garrison completely, breaking the siege of Nanjing.

The eastern campaign began in 9 February. Gen. Li Xiucheng of the rebel forces encircled the region of Jiangnan. They approached the Zhejiang provincial capital, Hangzhou, disguised as Qing troops. At Hangzhou, the 60,000 Taiping troops were outnumbered by Qing defenders, so they used several deception tricks such as placing hundreds of flags on a hill giving the impression of large numbers. The city walls were destroyed with explosives on 19 March, and the city was taken soon after. The Mayor of Hangzhou committed suicide after the loss.