Among the oldest of Britain's battleships at the time, Magnificent was a guard ship on the Humber when World War I broke out. She was then, together with her sister ship Hannibal, assigned to Scapa Flow as a guard ship. In 1915, she was stripped of her main armament, and later in that year was converted to a troopship for use in the Dardanelles Campaign. Returning to England in 1916, she was inactive until late 1917, at which time she was converted to an ammunition ship. She continued to serve in this role until 1921, at which time she was decommissioned before being scrapped the following year.
Magnificent was laid down at the Chatham Dockyard on 18 December 1893. She was launched a year and a day later, on 19 December 1894, after which fitting-out work commenced. She was commissioned into the Royal Navy another year later, in December 1895. The ship was 421 feet (128 m) long overall and had a beam of 75 ft (23 m) and a draft of 27 ft (8.2 m). She displaced up to 16,060 t (15,810 long tons; 17,700 short tons) at full combat load. Her propulsion system consisted of two 3-cylinder triple expansion engines powered by eight coal-fired cylindrical boilers. By 1907–1908, she was re-boilered with oil-fired models. Her engines provided a top speed of 16 knots (30 km/h; 18 mph) at 10,000 indicated horsepower (7,500 kW). The Majestics were considered good seaboats with an easy roll and good steamers, although they suffered from high fuel consumption. She had a crew of 672 officers and enlisted men.
The ship was armed with four BL 12-inch Mk VIII guns in twin turrets, one forward and one aft. The turrets were placed on pear-shaped barbettes; six of her sisters had the same arrangement, but her sisters Caesar and Illustrious and all future British battleship classes had circular barbettes. Magnificent also carried twelve QF 6-inch /40 guns. They were mounted in casemates in two gun decks amidships. She also carried sixteen QF 12-pounder guns and twelve QF 2-pounder guns. She was also equipped with five 18 in (460 mm) torpedo tubes, four of which were submerged in the ship's hull, with the last in a deck-mounted launcher. Magnificent and the other Majestic-class ships had 9 inches (229 mm) of Harvey armour, which allowed equal protection with less cost in weight compared to previous types of armour. This allowed Magnificent and her sisters to have a deeper and lighter belt than previous battleships without any loss in protection. The barbettes for the main battery were protected with 14 in (360 mm) of armor, and the conning tower had the same thickness of steel on the sides. The ship's armored deck was 2.5 to 4.5 in (64 to 114 mm) thick.
HMS Magnificent was commissioned at Chatham Dockyard on 12 December 1895 to relieve the battleship Empress of India as second flagship of the Channel Fleet. On 26 June 1897, she was present at the Fleet Review at Spithead for the Diamond Jubilee of Queen Victoria. Captain John Ferris was appointed in command in January 1899, and from February the following year she joined the Eastern division of the Channel Fleet, flying the flag of Rear-Admiral Arthur Dalrymple Fanshawe. On receiving word of the death of Queen Victoria on 21 January 1901 while stationed in Portsmouth, Magnificent flew the Royal Standard at half mast. Captain Arthur John Horsley was appointed in command in October 1900, and in June the following year she became flagship of Rear-Admiral Sir William Acland, second in command of the Channel Squadron. He relinquished the position one year later, and at sunset on 5 June 1902 struck his flag on board the Magnificent. Rear-Admiral Assheton Curzon-Howe, who had succeeded Acland, transferred to the vessel later the same month. She took part in the fleet review held at Spithead on 16 August 1902 for the coronation of King Edward VII.
By January 1904, the ship had become the flagship of the Channel Fleet. As a result of a reorganization in January 1905, the Channel Fleet became the Atlantic Fleet, and Magnificent accordingly became a part of the Atlantic Fleet. A gun explosion aboard Magnificent on 14 June 1905 resulted in 18 casualties. The explosion was caused by a faulty shell in one of the 6-inch guns; it failed to fire, and when the loader opened the breech, contact with the fresh air detonated the shell. On 15 November 1906, she ended her Atlantic Fleet service and was paid off at Devonport. Magnificent was commissioned into reserve on 16 November 1906, based at Chatham. During her reserve service, she was attached to the Gunnery School at Sheerness as a gunnery training ship in December 1906.