John Henry Rushworth Jellicoe was born at Southampton, England, on 5 December 1859, the son of John Henry Jellicoe, a master in the merchant service, and his wife, Lucy Henrietta Keele. At the age of six he attended a preparatory school, at 11 he went to Field House, Rottingdean, and at 12 (in 1872) he entered the Royal Navy. Later he qualified as a gunnery specialist. During a varied service he participated in the Egyptian war of 1882, survived the loss of the Victoria following a collision in 1893, and was badly wounded while leading a naval brigade during the Boxer rebellion in China in 1900. On 1 July 1902 he married Florence Gwendoline Cayzer, with whom he would have six children.
While serving at the Admiralty during the first decade of the century, Jellicoe was heavily involved in the development of the British battle fleet, as it adjusted to the demands of new technology and the threat posed by the growing German navy. During 1907 he was promoted to rear admiral and made a KCVO. After the outbreak of war in 1914 he took command of the Grand Fleet. At the battle of Jutland two years later he twice put the German fleet in extreme jeopardy, but was unable to defeat it decisively, an outcome that would become a matter of great controversy in Britain after the war. Jellicoe, who was appointed an OM soon after the battle, became First Sea Lord in December 1916. Again his tenure proved controversial as the Allies sought to counter Germany's unrestricted submarine campaign, and he was eventually dismissed in December 1917 because the British prime minister, David Lloyd George, was convinced that the Admiralty had been negligent. Even so, for his war services, he was raised to the peerage as Viscount Jellicoe of Scapa in January 1918, and in the following year was given a grant of £50,000 from the nation and promoted to the rank of admiral of the fleet.
In February 1919 Jellicoe was dispatched on a year-long mission to advise dominion governments on naval policy. Conveyed by the New Zealand, first to India and Australia, he reached New Zealand on 20 August 1919. During the next six weeks he visited ports throughout the country and carried out many social engagements, while preparing a three-volume report for the government. This emphasised the necessity of a Pacific fleet with adequate docking facilities to counter a possible threat from Japan, and set out ways in which New Zealand could contribute to the fleet. Financial stringency prevented the full implementation of his recommendations, but New Zealand did follow his suggestion in creating, in 1921, a New Zealand Division of the Royal Navy.
Even before his empire mission, Jellicoe had been keen to obtain the New Zealand governor-generalship, even declining, ostensibly on financial grounds, an offer of the Australian post. He saw such an appointment as a dignified and happy way of erasing the hurt caused by the manner of his dismissal as First Sea Lord. Moreover, he admired New Zealand's staunchly loyal attitude to empire. When arrangements for replacing Lord Liverpool fell through, the way was opened and he assumed office on 27 September 1920.
Jellicoe was regularly consulted by William Massey, the prime minister, about imperial affairs, and often took the initiative in providing comment on dispatches passing through his hands. On naval policy, which both he and Massey regarded as an imperial matter, his involvement breached the convention that the governor general not intervene in domestic politics; at the time, both Liberal and Labour parties were attacking the government's policy. Massey could with justification describe Jellicoe, who was always careful to give his advice discreetly, as 'an invaluable counsellor'. Their relationship was helped by their shared interest in British Israelism and, from 1922, Freemasonry. Jellicoe bolstered the government's resistance to any change in the constitutional framework of the British empire which might seem to weaken imperial unity. During the Chanak crisis of 1922, he prompted New Zealand's almost instant offer to send troops in support of the empire against Turkey.
A wider constitutional question was raised when he privately advised Massey to protest against the British Labour administration's decision in 1924 to end work on the Singapore naval base, the key to British power in the Pacific region. In making suggestions as to the wording of the cable to be sent to the imperial authorities in London, he took a stance against the British government, which he represented in the dominion.
Jellicoe was an active governor general, travelling widely throughout New Zealand and enthusiastically participating in sports such as cricket, golf, fishing and shooting. He was especially active in yachting, helping found the X-class boats and presenting the Sanders Cup; he took part in the first Sanders Cup series, and other national contests, and was patron of many yachting clubs. He also presented a challenge trophy for competition in rifle marksmanship between schools. The grand master of the Grand Lodge of New Zealand from 1922 to 1923, he served as patron of many charitable organisations and was especially interested in all ex-servicemen's matters.
So quickly did Jellicoe make an impact that Massey described him in 1921 as 'the most popular man we have had'. The fact that he was a man of action, who had risen to the top of his profession without the benefit of wealth or social standing, appealed to many New Zealanders. He was almost a working man's aristocrat. Dispensing with many formalities, he mixed easily with New Zealanders of all classes, who were impressed by his 'simple unassuming manner'. He also made a point of meeting with Maori. Even the Labour leader, H. E. Holland, in 1924 extolled his popularity and his appreciation for 'the atmosphere in which the rank and file of the people lived'. Jellicoe's strong imperial patriotism struck a chord with most New Zealanders, and he created a firm preference for distinguished servicemen as governors general.
The admiration was mutual. For Jellicoe, the incomparable scenery was complemented by the hospitality and loyalty of the people. By the end of his term he could profess, with sincerity, to 'love the country and the people'. It was with much reluctance that he departed on 26 November 1924. His governor-generalship was thought to have strengthened one of New Zealand's few formal links with Britain. Several geographical features recall his presence, including the channel between Little Barrier Island and Cape Rodney and a point on the eastern shoreline of Lake Taupo. A ward named after him at Napier Hospital was destroyed in the 1931 earthquake.
Shortly after Jellicoe's return to Britain, where he took up residence near Ventnor, on the Isle of Wight, he was advanced to an earldom. Massey had seen him as virtually a naval ambassador for the dominion, and Gordon Coates's government formalised this role by appointing Jellicoe as one of New Zealand's delegates to the inconclusive Geneva Naval Conference in 1927 – an arrangement that fellow delegate Sir James Parr later described enthusiastically as 'a great stroke for New Zealand, giving us a decided importance in the Conference'. Because of Jellicoe's strong opposition to further cuts to British naval strength, the British Labour government ensured that he was excluded from the London Naval Conference in 1930, though New Zealand's delegate, Sir Thomas Wilford, did use Jellicoe's views to buttress his arguments against the British policy.
Jellicoe was president of the British Legion from 1928 to 1932. He was actively involved in many organisations, including the Boy Scouts' Association and the National Rifle Association. He died in London on 20 November 1935, and was buried in St Paul's Cathedral, alongside Horatio Nelson and other naval heroes. He was survived by his wife, Florence, four daughters and a son.