The Battle of Fei River, also known as the Battle of Feishui, took place in the winter of 383 AD in China, where forces of the Di-led Former Qin dynasty were decisively defeated by the outnumbered army of the Eastern Jin dynasty. The location of the battle, the Fei River, no longer exists but is believed to have flowed through modern Lu'an, Anhui, near the Huai River. The battle is considered to be one of the most significant and pivotal battles in Chinese history. In the aftermath of the battle, the Former Qin fell into a massive civil war, resulting in its eventual collapse, ensuring the survival of Eastern Jin and subsequent Han-ruled regimes south of the Yangtze River.

Qin, known as the Former Qin and Fu Qin (苻秦) in historiography, was a dynastic state of China ruled by the Fu (Pu) clan of the Di peoples during the Sixteen Kingdoms period. Founded in the wake of the Later Zhao dynasty's collapse in 351, it completed the unification of northern China in 376 during the reign of Fu Jiān, being the only state of the Sixteen Kingdoms to achieve so. Its capital was Chang'an up to Fu Jiān's death in 385. The adjectival prefix "former" is used to distinguish it from the "Later Qin dynasty" (384–417).