Bayan (Russian: Баян) was the name ship of the four Bayan-class armoured cruisers built for the Imperial Russian Navy in the first decade of the 20th century. The ship had to be built in France because there was no available capacity in Russia. Bayan was assigned to the First Pacific Squadron after completion and based at Port Arthur from the end of 1903. She suffered minor damage during the Battle of Port Arthur at the beginning of the Russo-Japanese War of 1904–05 and supported destroyers as they patrolled outside the harbour. After bombarding Japanese positions in July 1904, the ship struck a mine and was out of action for the next several months. Bayan was sunk during the Siege of Port Arthur and was then salvaged by the Japanese after the war.

Renamed Aso by the Imperial Japanese Navy (IJN) she served as a training ship after extensive repairs. The ship was converted into a minelayer in 1917 and was decommissioned in 1930 to serve as a target ship. She was eventually sunk as a target in 1932.

Unlike previous Russian armoured cruisers, the Bayan-class ships were designed as scouts for the fleet. They were 449 feet 7 inches (137.0 m) long overall and 443 feet (135.0 m) between perpendiculars. They had a maximum beam of 57 feet 6 inches (17.5 m), a draft of 22 feet (6.7 m) and displaced 7,802 long tons (7,927 t). The ships had a crew of 573 officers and men.

The Bayan class had two vertical triple-expansion steam engines, each driving a single propeller shaft using steam provided by 26 Belleville boilers. Designed for a total of 16,500 indicated horsepower (12,304 kW) intended to propel the cruisers at 21 knots (39 km/h; 24 mph), the engines actually developed 17,400 ihp (13,000 kW) during Bayan's sea trials in October 1902 and drove the ship to a maximum speed of 20.9 knots (38.7 km/h; 24.1 mph). She could carry a maximum of 1,100 long tons (1,118 t) of coal, which gave her a range of 3,900 nautical miles (7,200 km; 4,500 mi) at 10 knots (19 km/h; 12 mph).

Bayan's main armament consisted of two 8-inch (203 mm) 45-calibre guns in single turrets fore and aft of the superstructure. Her eight 6-inch (152 mm) guns were mounted in casemates on the sides of the ship's hull. Anti-torpedo boat defence was provided by twenty 75-millimetre (3.0 in) 50-calibre guns; eight of these were mounted in casemates on the side of the hull and in the superstructure. The remaining guns were located above the six-inch gun casemates in pivot mounts with gun shields. Bayan also mounted eight 47-millimetre (1.9 in) and two 37-millimetre (1.5 in) Hotchkiss guns. The ship had two submerged 15-inch (381 mm) torpedo tubes, one on each broadside.

The ship used Harvey armour throughout. Her waterline belt was 7.9 inches (200 mm) thick over her machinery spaces. Fore and aft, it reduced to 3.9 inches (100 mm). The upper armour strake and the armour protecting the casemates was 2.4 inches (60 mm) thick. The thickness of the armoured deck was 2 inches (50 mm); over the central battery it was a single plate, but elsewhere it consisted of a 1.2-inch (30 mm) plate over two 0.39-inch (10 mm) plates. The gun turret sides were protected by 5.9 inches (150 mm) of armour and their roofs were 1.2 inches thick. The barbettes were protected by armour plates 6.7-inch (170 mm) thick. The sides of the conning tower were 6.3 inches (160 mm) thick.

Bayan, named after the bard Boyan, had to be ordered in May 1898 from the French shipyard Forges et Chantiers de la Méditerranée in La Seyne-sur-Mer because there was no capacity available in Russian shipyards. The ship was laid down in February 1899 and launched on 12 June 1900. Bayan was completed in February 1903 and, under the command of Captain 1st Rank Robert Wiren, made port visits in Greece, Italy and North Africa before sailing for Kronstadt. Arriving in April 1903, she was only there for several months before departing for Port Arthur on 7 August. Together with the French-built battleship Tsesarevich, Bayan arrived on 2 December and they were both assigned to the First Pacific Squadron.

On the night of 8/9 February 1904, the IJN launched a surprise attack on the Russian fleet at Port Arthur. Bayan was not hit by the initial torpedo-boat incursion and sortied the following morning when the Combined Fleet, commanded by Vice Admiral Tōgō Heihachirō, attacked. Tōgō had expected the surprise night attack by his ships to be much more successful than it was, anticipating that the Russians would be badly disorganized and weakened, but they had recovered from their surprise and were ready for his assault. The Japanese vessels had been spotted by the protected cruiser Boyarin, which was patrolling offshore, and alerted the Russian defences. Tōgō chose to attack the Russian coastal defences with his main armament and engage the ships with his secondary guns. Splitting his fire proved to be a poor decision as the Japanese eight-inch (203 mm) and six-inch guns inflicted inconsequential damage on the Russian ships, which concentrated all their fire on their opponents with some effect. Bayan suffered superficial damage from nine hits and numerous splinters; 6 crewmen were killed and 35 injured. The ship fired 28 eight-inch, 100 six-inch and 160 seventy-five-millimetre shells during the battle.