The Battle of the Yalu River (simplified Chinese: 黄海海战; traditional Chinese: 黃海海戰; pinyin: Huáng Hǎi Hǎizhàn; Japanese: 黄海海戦, romanized: Kōkai-kaisen; lit. 'Naval Battle of the Yellow Sea') was the largest naval engagement of the First Sino-Japanese War, and took place on 17 September 1894, the day after the Japanese victory at the land Battle of Pyongyang. It involved ships from the Imperial Japanese Navy and the Chinese Beiyang Fleet.

The battle is also known by a variety of names: Battle of Haiyang Island, Battle of Dadonggou, Battle of the Yellow Sea and Battle of Yalu, after the geographic location of the battle, which was in the Yellow Sea off the mouth of the Yalu River and not in the river itself. There is no agreement among contemporary sources on the exact numbers and composition of each fleet, but both were of a similar size, and the battle is considered to be one of the Imperial Japanese Navy's greatest victories.