He was baptised in the large drawing room of Frogmore House on 17 July 1900 by the Dean of Windsor, Philip Eliot. His godparents were Queen Victoria, Nicholas II of Russia (represented by his father) and Prince Francis Joseph of Battenberg (represented by Lord Edward Clinton).

Mountbatten was educated at home for the first 10 years of his life: he was then sent to Lockers Park School in Hertfordshire and on to the Royal Naval College, Osborne in May 1913. In childhood he visited the Imperial Court of Russia at St Petersburg and became intimate with the doomed Russian Imperial Family, harbouring romantic feelings towards his maternal first cousin Grand Duchess Maria Nikolaevna, whose photograph he kept at his bedside for the rest of his life.

Mountbatten was posted as midshipman to the battlecruiser HMS Lion in July 1916 and, after seeing action in August 1916, transferred to the battleship HMS Queen Elizabeth during the closing phases of the First World War. In June 1917, when the royal family stopped using their German names and titles and adopted the more British-sounding "Windsor", Prince Louis of Battenberg became Louis Mountbatten, and was created Marquess of Milford Haven. His second son acquired the courtesy title Lord Louis Mountbatten and was known as Lord Louis until he was created a peer in 1946. He paid a visit of ten days to the Western Front, in July 1918.

From the time of his birth at Frogmore House in the Home Park, Windsor, Berkshire until 1917, when he and several other relations of King George V dropped their German styles and titles, Mountbatten was known as His Serene Highness Prince Louis of Battenberg. He was the youngest child and the second son of Prince Louis of Battenberg and his wife Princess Victoria of Hesse and by Rhine. His maternal grandparents were Louis IV, Grand Duke of Hesse, and Princess Alice of the United Kingdom, who was a daughter of Queen Victoria and Prince Albert of Saxe-Coburg and Gotha. His paternal grandparents were Prince Alexander of Hesse and by Rhine and Julia, Princess of Battenberg.

He was appointed executive officer (second-in-command) of the small warship HMS P.31 on 13 October 1918 and was promoted sub-lieutenant on 15 January 1919. HMS P.31 took part in the Peace River Pageant on 4 April 1919. Mountbatten attended Christ's College, Cambridge for two terms, starting in October 1919, where he studied English literature (including John Milton and Lord Byron) in a programme that was specially designed for ex-servicemen. He was elected for a term to the Standing Committee of the Cambridge Union Society, and was suspected of sympathy for the Labour Party, then emerging as a potential party of government for the first time.

He was posted to the battlecruiser HMS Renown in March 1920 and accompanied Edward, Prince of Wales, on a royal tour of Australia in her. He was promoted lieutenant on 15 April 1920. HMS Renown returned to Portsmouth on 11 October 1920. Early in 1921 Royal Navy personnel were used for civil defence duties as serious industrial unrest seemed imminent. Mountbatten had to command a platoon of stokers, many of whom had never handled a rifle before, in northern England. He transferred to the battlecruiser HMS Repulse in March 1921 and accompanied the Prince of Wales on a Royal tour of India and Japan. Edward and Mountbatten formed a close friendship during the trip. Mountbatten survived the deep defence cuts known as the Geddes Axe. Fifty-two percent of the officers of his year had had to leave the Royal Navy by the end of 1923; although he was highly regarded by his superiors, it was rumoured that wealthy and well-connected officers were more likely to be retained. He was posted to the battleship HMS Revenge in the Mediterranean Fleet in January 1923.

Mountbatten was married on 18 July 1922 to Edwina Cynthia Annette Ashley, daughter of Wilfred william Ashley, later 1st Baron Mount Temple, himself a grandson of the 7th Earl of Shaftesbury. She was the favourite granddaughter of the Edwardian magnate Sir Ernest Cassel and the principal heir to his fortune. There followed a honeymoon tour of European royal courts and America which included a visit to Niagara Falls (because "all honeymooners went there").

Lord and Lady Mountbatten had two daughters: Patricia Knatchbull, 2nd Countess Mountbatten of Burma (born 14 February 1924, died 13 June 2017), sometime lady-in-waiting to Queen Elizabeth II, and Lady Pamela Hicks (born 19 April 1929), who accompanied them to India in 1947–48 and was also sometime lady-in-waiting to the Queen.

Mountbatten admitted "Edwina and I spent all our married lives getting into other people's beds." He maintained an affair for several years with Yola Letellier, the wife of Henri Letellier, publisher of Le Journal and mayor of Deauville (1925–28). Yola Letellier's life story was the inspiration for Colette's novel Gigi. Edwina and Jawaharlal Nehru became intimate friends after Indian Independence. During the summers, she would frequent the prime minister's house so she could lounge about on his veranda during the hot Delhi days. Personal correspondence between the two reveals a satisfying yet frustrating relationship. Edwina states in one of her letters. "Nothing that we did or felt would ever be allowed to come between you and your work or me and mine – because that would spoil everything."

Pursuing his interests in technological development and gadgetry, Mountbatten joined the Portsmouth Signals School in August 1924 and then went on briefly to study electronics at the Royal Naval College, Greenwich. Mountbatten became a Member of the Institution of Electrical Engineers (IEE), now the Institution of Engineering and Technology (IET), which annually awards the Mountbatten Medal for an outstanding contribution, or contributions over a period, to the promotion of electronics or information Technology and their application. He was posted to the battleship HMS Centurion in the Reserve Fleet in 1926 and became Assistant Fleet Wireless and Signals Officer of the Mediterranean Fleet under the command of Admiral Sir Roger Keyes in January 1927. Promoted lieutenant-commander on 15 April 1928, he returned to the Signals School in July 1929 as Senior Wireless Instructor. He was appointed Fleet Wireless Officer to the Mediterranean Fleet in August 1931, and having been promoted commander on 31 December 1932, was posted to the battleship HMS Resolution.

Like many members of the royal family, Mountbatten was an aficionado of polo. He received U.S. patent 1,993,334 in 1931 for a polo stick. Mountbatten introduced the sport to the Royal Navy in the 1920s, and wrote a book on the subject. He also served as Commodore of Emsworth Sailing Club in Hampshire from 1931.

In 1934, Mountbatten was appointed to his first command – the destroyer HMS Daring. His ship was a new destroyer, which he was to sail to Singapore and exchange for an older ship, HMS Wishart. He successfully brought Wishart back to port in Malta and then attended the funeral of King George V in January 1936. Mountbatten was appointed a Personal Naval Aide-de-Camp to King Edward VIII on 23 June 1936, and, having joined the Naval Air Division of the Admiralty in July 1936, he attended the coronation of King George VI and Queen Elizabeth in May 1937. He was promoted Captain on 30 June 1937 and was then given command of the destroyer HMS Kelly in June 1939.

Mountbatten's qualification for offering advice to this particular heir to the throne was unique; it was he who had arranged the visit of King George VI and Queen Elizabeth to Dartmouth Royal Naval College on 22 July 1939, taking care to include the young Princesses Elizabeth and Margaret in the invitation, but assigning his nephew, Cadet Prince Philip of Greece, to keep them amused while their parents toured the facility. This was the first recorded meeting of Charles's Future parents. But a few months later, Mountbatten's efforts nearly came to naught when he received a letter from his sister Alice in Athens informing him that Philip was visiting her and had agreed to permanently repatriate to Greece. Within days, Philip received a command from his cousin and sovereign, King George II of Greece, to resume his naval career in Britain which, though given without explanation, the young Prince obeyed.

On the night of 9/10 May 1940, Kelly was torpedoed amidships by a German E-boat S 31 off the Dutch coast, and Mountbatten thereafter commanded the 5th Destroyer Flotilla from the destroyer HMS Javelin. He rejoined Kelly in December 1940, by which time the torpedo damage had been repaired.

Mountbatten was a favourite of Winston Churchill. On 27 October 1941 Mountbatten replaced Roger Keyes as Chief of Combined Operations and promoted commodore.

As commander of Combined Operations, Mountbatten and his staff planned the highly successful Bruneval raid, which gained important information and also captured part of a German Würzburg radar installation and one of the machine's technicians on 27 February 1942. It was Mountbatten who recognized that surprise and speed were essential to ensure the radar was captured, and saw that an airborne assault was the only viable method. He was in large part responsible for the planning and organisation of The Raid at St. Nazaire in mid-1942, an operation which put out of action one of the most heavily defended docks in Nazi-occupied France until well after war's end, the ramifications of which contributed to allied supremacy in the Battle of the Atlantic. After these two successes came the Dieppe Raid of 19 August 1942. He was central in the planning and promotion of the raid on the port of Dieppe. The raid was a marked failure, with casualties of almost 60%, the great majority of them Canadians. Following the Dieppe raid Mountbatten became a controversial figure in Canada, with the Royal Canadian Legion distancing itself from him during his visits there during his later career. His relations with Canadian veterans, who blamed him for the losses, "remained frosty" after the war.

In August 1943, Churchill appointed Mountbatten the Supreme Allied Commander South East Asia Command (SEAC) with promotion to acting full admiral. His less practical ideas were sidelined by an experienced planning staff led by Lieutenant-Colonel James Allason, though some, such as a proposal to launch an amphibious assault near Rangoon, got as far as Churchill before being quashed.

During his time as Supreme Allied Commander of the Southeast Asia Theatre, his command oversaw the recapture of Burma from the Japanese by General william Slim. A personal high point was the receipt of the Japanese surrender in Singapore when British troops returned to the island to receive the formal surrender of Japanese forces in the region led by General Itagaki Seishiro on 12 September 1945, codenamed Operation Tiderace. South East Asia Command was disbanded in May 1946 and Mountbatten returned home with the substantive rank of rear-admiral.

Since Mountbatten had no sons, when he was created Viscount Mountbatten of Burma, of Romsey in the County of Southampton on 27 August 1946 and then Earl Mountbatten of Burma and Baron Romsey, in the County of Southampton on 28 October 1947, the Letters Patent were drafted such that in the event he left no sons or issue in the male line, the titles could pass to his daughters, in order of seniority of birth, and to their male heirs respectively.

When India and Pakistan attained independence at midnight on the night of 14–15 August 1947, Mountbatten remained in New Delhi for 10 months, serving as India's first governor general until June 1948. On Mountbatten's advice, India took the issue of Kashmir to the newly formed United Nations in January 1948. The issue of Kashmir would become a lasting thorn in his legacy, one that is not resolved to this day. Accounts differ on the Future Mountbatten desired for Kashmir. Pakistani accounts suggest that Mountbatten favored the accession of Kashmir to India citing his close relationship to Nehru. Mountbatten's own account says that he simply wanted the maharaja Hari Singh to make up his mind. The viceroy made several attempts to mediate between the Congress Leaders, Muhammad Ali Jinnah and Hari Singh on issues relating to the accession of Kashmir though he was largely unsuccessful in resolving the conflict. After the tribal invasion of Kashmir, it was on his suggestion that India moved to secure the accession of Kashmir from Hari Singh before sending in military forces for his defence.

After India, Mountbatten served as commander of the 1st Cruiser Squadron in the Mediterranean Fleet and, having been granted the substantive rank of vice-admiral on 22 June 1949, he became Second-in-Command of the Mediterranean Fleet in April 1950. He became Fourth Sea Lord at the Admiralty in June 1950. He then returned to the Mediterranean to serve as Commander-in-Chief, Mediterranean Fleet and NATO Commander Allied Forces Mediterranean from June 1952. He was promoted to the substantive rank of full admiral on 27 February 1953. In March 1953, he was appointed Personal Aide-de-Camp to the Queen.

From 1954 until 1959 he was First Sea Lord, a position that had been held by his father, Prince Louis of Battenberg, some forty years earlier. Thereafter he served as Chief of the Defence Staff until 1965, making him the longest serving professional head of the British Armed Forces to date. During this period Mountbatten also served as Chairman of the NATO Military Committee for a year.

Mountbatten served his final posting at the Admiralty as First Sea Lord and Chief of the Naval Staff from April 1955 to July 1959, the position which his father had held some forty years prior. This was the first time in Royal Naval history that a father and son had both attained such high rank. He was promoted to Admiral of the Fleet on 22 October 1956.

While serving as First Sea Lord, his primary concerns dealt with devising plans on how the Royal Navy would keep shipping lanes open if Britain fell victim to a nuclear attack. Today, this seems of minor importance but at the time few people comprehended the potentially limitless destruction nuclear weapons possess and the ongoing dangers posed by the fallout. Military commanders did not understand the physics involved in a nuclear explosion. This became evident when Mountbatten had to be reassured that the fission reactions from the Bikini Atoll tests would not spread through the oceans and blow up the planet. As Mountbatten became more familiar with this new form of weaponry, he increasingly grew opposed to its use in combat yet at the same time he realised the potential nuclear Energy had, especially with regards to submarines. Mountbatten expressed his feelings towards the use of nuclear weapons in combat in his article "A Military Commander Surveys The Nuclear Arms Race", which was published shortly after his death in International Security in the winter of 1979–80. After leaving the Admiralty, Lord Mountbatten took the position of Chief of the Defence Staff. He served in this post for six years during which he was able to consolidate the three Service departments of the military branch into a single Ministry of Defence. Mountbatten was appointed Colonel of the Life Guards, Gold Stick in Waiting and Life Colonel Commandant of the Royal Marines in 1965. He was Governor of the Isle of Wight from 20 July 1965 and then the first Lord Lieutenant of the Isle of Wight from 1 April 1974.

From 1967 until 1978, Mountbatten was President of the United World Colleges Organisation, then represented by a single college: that of Atlantic College in South Wales. Mountbatten supported the United World Colleges and encouraged heads of state, politicians and personalities throughout the world to share his interest. Under Mountbatten's presidency and personal involvement, the United World College of South East Asia was established in Singapore in 1971, followed by the United World College of the Pacific (now known as the Lester B Pearson United World College of the Pacific) in Victoria, British Columbia, in 1974. In 1978, Mountbatten passed the presidency of the college to his great-nephew, the Prince of Wales.

Peter Wright, in his book Spycatcher, claimed that in May 1968 Mountbatten attended a private meeting with press baron Cecil King, and the Government's Chief Scientific Adviser, Solly Zuckerman. Wright alleged that "up to thirty" MI5 officers had joined a secret campaign to undermine the crisis-stricken Labour government of Harold Wilson and that King was an MI5 agent. In the meeting, King allegedly urged Mountbatten to become the leader of a government of national salvation. Solly Zuckerman pointed out that it was "rank treachery", and the idea came to nothing because of Mountbatten's reluctance to act.

In 1969 Mountbatten participated in a 12-part autobiographical television series Lord Mountbatten: A Man for the Century, also known as The Life and Times of Lord Mountbatten, produced by Associated-Rediffusion and scripted by Historian John Terraine. The episodes were:

In 1974, Mountbatten began corresponding with Charles about a potential marriage to his granddaughter, Hon. Amanda Knatchbull. It was about this time he also recommended that the 25-year-old Prince get on with "sowing some wild oats". Charles dutifully wrote to Amanda's mother (who was also his godmother), Lady Brabourne, about his interest. Her answer was supportive, but advised him that she thought her daughter still rather young to be courted.

In February 1975, Charles visited New Delhi to play polo and was shown around Rashtrapati Bhavan, the former Viceroy's House, by Mountbatten.

On 27 April 1977, shortly before his 77th birthday, Mountbatten became the first member of the Royal Family to appear on the TV guest show This Is Your Life.

Mountbatten usually holidayed at his summer home, Classiebawn Castle, in Mullaghmore, a small seaside village in County Sligo, Ireland. The village was only 12 miles (19 km) from the border with Northern Ireland and near an area known to be used as a cross-border refuge by IRA members. In 1978, the IRA had allegedly attempted to shoot Mountbatten as he was aboard his boat, but "choppy seas had prevented the sniper Li Ning up his target".

Thomas McMahon, who had been arrested two hours before the bomb detonated at a Garda checkpoint between Longford and Granard on suspicion of driving a stolen vehicle, was tried for the assassinations in Ireland, and convicted on 23 November 1979 by forensic evidence supplied by James O'Donovan that showed flecks of paint from the boat and traces of nitroglycerine on his clothes. He was released in 1998 under the terms of the Good Friday Agreement.

On hearing of Mountbatten's death the then Master of the Queen's Music, Malcolm Williamson, was moved to write the Lament in Memory of Lord Mountbatten of Burma for violin and string orchestra. The 11-minute work was given its first performance on 5 May 1980 by the Scottish Baroque Ensemble, conducted by Leonard Friedman.

Mountbatten took pride in enhancing intercultural understanding and in 1984, with his elder daughter as the patron, the Mountbatten Institute was developed to allow young adults the opportunity to enhance their intercultural appreciation and experience by spending time abroad.

In 2006, the BBC documentary The Plot Against Harold Wilson alleged that there had been another plot involving Mountbatten to oust Wilson during his second term in office (1974–76). The period was characterised by high inflation, increasing unemployment and widespread industrial unrest. The alleged plot revolved around right-wing former military figures who were supposedly building private armies to counter the perceived threat from trade unions and the Soviet Union. They believed that the Labour Party, which was (and still is) partly funded by affiliated trade unions, was unable and unwilling to counter these developments and that Wilson was either a Soviet agent or at the very least a Communist sympathiser – claims Wilson strongly denied. The documentary alleged that a coup was planned to overthrow Wilson and replace him with Mountbatten using the private armies and sympathisers in the military and MI5.

The first official history of MI5, The Defence of the Realm (2009), tacitly confirmed that there was a plot against Wilson and that MI5 did have a file on him. Yet it also made clear that the plot was in no way official and that any activity centred on a small group of discontented officers. This much had already been confirmed by former cabinet secretary Lord Hunt, who concluded in a secret inquiry conducted in 1996 that "there is absolutely no doubt at all that a few, a very few, malcontents in MI5...a lot of them like Peter Wright who were right-wing, malicious and had serious personal grudges – gave vent to these and spread damaging malicious stories about that Labour government."

Mountbatten was a strong influence in the upbringing of his grand-nephew, Charles, Prince of Wales, and later as a mentor – "Honorary Grandfather" and "Honorary Grandson", they fondly called each other according to the Jonathan Dimbleby biography of the Prince – though according to both the Ziegler biography of Mountbatten and the Dimbleby biography of the Prince, the results may have been mixed. He from time to time strongly upbraided the Prince for showing tendencies towards the idle pleasure-seeking dilettantism of his predecessor as Prince of Wales, King Edward VIII, whom Mountbatten had known well in their youth. Yet he also encouraged the Prince to enjoy the bachelor life while he could and then to marry a young and inexperienced girl so as to ensure a stable married life.

In May 2015, during a meeting with Prince Charles, Adams did not apologize. He later said in an interview, "I stand over what I said then. I'm not one of those people that engages in revisionism. Thankfully the war is over".