The Battle of the Japanese Sea was a minor naval enagement during the Russo-Japanese War. It is also called the Battle of Ulsan. It was fought on August 14, 1904, four days after the naval Battle of the Yellow Sea.

The Russian fleet made up of the armoured cruisers Rossiia, Gromoboi and Ryurik of Vladivostok Cruiser Unit, that raided against Japanese sea commerce in the first stage of the war. That time, under the command of Rear Admiral Yessen, they sortied from Vladivostok on August 10 to support the break-out attempt of the First Pacific Squadron from Port Arthur which led to the Battle of the Yellow Sea.

At dawn on August 14, the small Russian fleet were met by a Japanese fleet making up of more modern armoured cruisers Izumo, Adzuma, Tokiwa, Iwate, and two protected cruisers Naniwa and Takachiho under the command of Vice Admiral Kamimura, near Ulsan island.

The Japanese fired first. After one hour of an artillery duel, Ryurik was heavily damaged and lost steering ability. During the next two hours, two remaining cruisers were fighting with the Japanese, trying to cover Ryurik. Since they were damaged themselves, Yessen finally decided to leave Ryurik and save the other ships, and headed towards Vladivostok. Japanese armoured cruisers chased them for some time, but finally ceased chasing. The damage to the Japanese warships was slight, mostly to Iwate.

At that time, Ryrik continued fighting with protected cruisers, suffering heavy crew losses. Finally, disabled ship was scuttled by the crew.

Despite the Japanese failure to destroy the two remaining Russian cruisers, the Russian Vladivostok Cruiser Unit did not resume their raiding activities in the Sea of Japan and as a result, the Japanese were left unchallenged command of the Yellow Sea.