Requin was an ironclad barbette ship built for the French Navy in the late 1870s and early 1880s. She was last member of the four-ship Terrible class. They were built as part of a fleet plan started in 1872, which by the late 1870s had been directed against a strengthening Italian fleet. The ships were intended for coastal operations, and as such had a shallow draft and a low freeboard, which greatly hampered their seakeeping and thus reduced their ability to be usefully employed outside of coastal operations after entering service. Armament consisted of a pair of 420 mm (16.5 in) guns in individual barbettes, the largest-caliber gun ever mounted on a French capital ship. Requin was laid down in 1878 and was completed in 1887.

Unlike her sister ships that served in the Mediterranean Fleet, Requin spent her early career in the Northern Squadron in the English Channel. In 1891, the unit was sent to visit Britain and Russia. She was withdrawn from service in 1896 to be modernized with new armament, propulsion system, and armor. Work was completed in 1901 and the next year she returned to service as a guard ship based in Cherbourg. She was the only member of the class to see action during World War I, during which she was stationed in the Suez Canal to defend the waterway against attacks from the Ottoman Empire. She helped to repel a major attack in February 1915, and supported Allied operations along the coast of Ottoman Palestine in 1917. She was briefly used as a training ship after the war, before being broken up in 1921.

The Terrible class of barbette ships was designed in the late 1870s as part of a naval construction program that began under the post-Franco-Prussian War fleet plan of 1872. By 1877, the Italian fleet under Benedetto Brin had begun building powerful new ironclads of the Duilio and Italia classes, which demanded a French response, beginning with the ironclad Amiral Duperré of 1877. In addition, the oldest generation of French ironclads, built in the early-to-mid 1860s, were in poor condition and necessitated replacement. The Terrible class was intended to replace old monitors that had been built for coastal defense. Ships of the class were based on the Amiral Baudin-class ironclads, but reduced in size to allow them to operate in shallower waters. They nevertheless carried a larger main battery of two 42-centimeter (16.5 in) guns.

After entering service, the Terrible-class ships were found to have very poor seakeeping as a result of their shallow draft and insufficient freeboard, even in the relatively sheltered waters of the Mediterranean Sea. The Navy had little use for the ships, and through the 1880s and 1890s, a series of French naval ministers sought to find a role for the vessels, along with another ten coastal-defense type ironclads built during that period. The ships frequently alternated between the Mediterranean Squadron and the Northern Squadron, the latter stationed in the English Channel, but neither location suited their poor handling.

Requin was 88.25 m (289 ft 6 in) long overall, with a beam of 17.78 m (58 ft 4 in) and an average draft of 7.74 m (25 ft 5 in). The vessel displaced 7,767.2 metric tons (7,644.5 long tons; 8,561.9 short tons) and had a relatively low freeboard. Her superstructure was minimal and consisted of a small conning tower. She was fitted with a pair of tripod masts equipped with spotting tops for her main battery guns. The ship's crew consisted of 373 officers and enlisted men.

Her propulsion machinery consisted of two compound steam engines that drove a pair of screw propellers. Steam was provided by twelve coal-burning fire-tube boilers that were vented through a pair of funnels that were placed side by side, just aft of the conning tower. The engines were rated to produce 6,000 indicated horsepower (4,500 kW) for a top speed of 14.5 to 15 knots (26.9 to 27.8 km/h; 16.7 to 17.3 mph). The ship had a storage capacity of 394 t (388 long tons; 434 short tons) of coal, which allowed her to steam for 1,678 nautical miles (3,108 km; 1,931 mi) at a speed of about 11 knots (20 km/h; 13 mph).

Her main armament consisted of two Canon de 42 cm modèle 1875 22-caliber guns, one forward and one aft, mounted on the centerline in barbettes. They were the largest-bore guns ever carried by a French capital ship. These were supported by a secondary battery of four 100 mm (3.9 in) 26.2-cal. M1881 guns carried in individual pivot mounts with gun shields. For defense against torpedo boats, she carried two 65 mm (2.6 in) guns, two 47 mm (1.9 in) M1885 quick-firing guns, one 47 mm Hotchkiss revolver cannon, and ten 37 mm (1.5 in) revolver cannon, all in individual mounts. Her armament was rounded out with four 356 mm (14 in) torpedo tubes in the hull above the waterline, two tubes per side.

The ship was protected with compound armor; her belt was 500 mm (19.7 in) thick amidships, where it protected the ship's propulsion machinery spaces and ammunition magazines. On either end of the central portion, the belt was reduced to 300 mm (11.8 in), and it extended for the entire length of the hull. At even normal loading, the belt was nearly submerged entirely, reducing its effectiveness significantly. Her armor deck was 80 mm (3.1 in) layered on 16 mm (0.63 in) of hull plating, and it curved downward at the sides. The barbettes for the main battery were 450 mm (18 in) thick, layered on top of 30 mm (1.2 in) hull plating, and the tubular supports connecting them to the ammunition magazines were 200 mm (7.9 in). They were fitted with 17 mm (0.7 in) hoods to protect the gun crews from shell fragments. Her conning tower armor was 25 mm (0.98 in) thick, as were the shields for the 100 mm guns.