The Battle of Liaoyang (August 24, 1904 - September 4, 1904) was one of the major battles of the Russo-Japanese War.

It was fought on the Mukden–Port Arthur railway, south of the confluence of the Taizu and Liao rivers in Manchuria. Both the Russian armies and Japanese armies were attempting to inflict a decisive defeat on the other. The battle began on August 25 with the Russian armies, 150,000 strong, attemping to turn the flanks of the Japanese First, Second and Third Armies totaling 125,000 men. After a hard-fought action, General Alexei Kuropatkin, commander-in-chief of the Russian armies, belived that he had been beaten and withdrew towards Mukden.

The Russian armies suffered about 17,900 casualties, the majority of those being captured or missing. The Japanese suffered heaver casualties of 23,615 killed, wounded or captured. However, despite the Japanese armies being in worse shape then the Russians afterwards, they could claim victory because of the Russians quiting the battlefield.

The dearly-won Japanese victory at Liaoyang (now, and historically, a Chinese city) and the fall of Port Arthur contributed to the Russian defeat the next year at the Battle of Mukden, which in turn helped start the Revolution of 1905.