HMS Donegal was one of 10 Monmouth-class armoured cruisers built for the Royal Navy in the first decade of the 20th century. She was initially assigned to the 1st Cruiser Squadron upon completion in 1903 and ran aground en route to the China Station in 1906.

She was briefly placed in reserve after repairs before she was assigned to the Home Fleet in 1907. She joined the 4th Cruiser Squadron on the North America and West Indies Station in 1909 before returning home for an assignment with the Training Squadron in 1912. Donegal was reduced to reserve before World War I began in August 1914 as part of the Third Fleet

Refitting at the beginning of the war, she was then assigned to Sierra Leone for convoy protection duties as part of the 5th Cruiser Squadron. She was transferred to several different cruiser squadrons of the Grand Fleet in 1915 where she escorted convoys to Archangelsk, Russia. In mid-1916 she was assigned to convoy escort duties in the Atlantic. Donegal rejoined the 4th Cruiser Squadron on North America and West Indies Station in 1917 and continued with convoy duties until the end of the war. Donegal was sold for scrap in 1920.