Upon Queen Victoria's death, Beatrice began the momentous task of transcribing and editing her mother's journals, which had been kept since 1831. The hundreds of volumes contained the Queen's personal views of the day-to-day Business of her life and included personal and family matters as well as matters of state.

Beatrice was born at Buckingham Palace. She was the fifth daughter and youngest of the nine children of the reigning British monarch, Queen Victoria, and her husband, Prince Albert of Saxe-Coburg and Gotha (later the Prince Consort). The birth caused controversy when it was announced that Queen Victoria would seek relief from the pains of delivery through the use of chloroform administered by Dr John Snow. Chloroform was considered dangerous to mother and child and was frowned upon by the Church of England and the medical authorities. Queen Victoria was undeterred and used "that blessed chloroform" for her last pregnancy. A fortnight later, Queen Victoria reported in her journal, "I was amply rewarded and forgot all I had gone through when I heard dearest Albert say 'It's a fine child, and a girl!'" Albert and Queen Victoria chose the names Beatrice Mary Victoria Feodore: Mary after Princess Mary, Duchess of Gloucester, the last surviving child of King George III of the United Kingdom; Victoria after the Queen; and Feodore after Feodora, Princess of Hohenlohe-Langenburg, the Queen's older half-sister. She was baptised in the private chapel at Buckingham Palace on 16 June 1857. Her godparents were the Duchess of Kent (maternal grandmother); the Princess Royal (eldest sister); and the Prince Frederick of Prussia (her Future brother-in-law).

In 1858, Beatrice and the three younger of her sisters were granted use of the royal arms, with an inescutcheon of the shield of Saxony and differenced by a label of three points argent. On Beatrice's arms, the outer points bore roses gules, and the centre a heart gules. In 1917, the inescutcheon was dropped by royal warrant from George V.

In March 1861, Queen Victoria's mother Victoria, Duchess of Kent, died at Frogmore. The Queen broke down in grief and guilt over their estrangement at the beginning of her reign. Beatrice tried to console her mother by reminding her that the Duchess of Kent was "in heaven, but Beatrice hopes she will return". This comfort was significant because Queen Victoria had isolated herself from her children except the eldest unmarried, Princess Alice, and Beatrice. Queen Victoria again relied on Beatrice and Alice after the death of Albert, of typhoid fever, on 14 December.

After the death of the Prince Imperial, Beatrice's brother, Albert Edward, the Prince of Wales, suggested that she marry their sister Alice's widower, Louis IV, the Grand Duke of Hesse, who had lost his wife to diphtheria in 1878. Albert Edward argued that Beatrice could act as replacement mother for Louis's young children and spend most of her time in England looking after her mother. He further suggested the Queen could oversee the upbringing of her Hessian grandchildren with greater ease. However, at the time, it was forbidden by law for Beatrice to marry her sister's widower. This was countered by the Prince of Wales, who vehemently supported passage by the Houses of Parliament of the Deceased Wife's Sister Bill, which would have removed the obstacle. Despite popular support for this measure and although it passed in the House of Commons, it was rejected by the House of Lords because of opposition from the Lords Spiritual. Although the Queen was disappointed that the bill had failed, she was happy to keep her daughter at her side.

Although the Queen was set against Beatrice marrying anyone in the expectation that she would always stay at home with her, a number of possible suitors were put forward before Beatrice's marriage to Prince Henry of Battenberg. One of these was Napoléon Eugéne, the French Prince Imperial, son and heir of the exiled Emperor Napoleon III of France and his wife, Empress Eugénie. After Prussia defeated France in the Franco-Prussian War, Napoleon was deposed and moved his family to England in 1870. After the Emperor's death in 1873, Queen Victoria and Empress Eugénie formed a close attachment, and the newspapers reported the imminent engagement of Beatrice to the Prince Imperial. These rumours ended with the death of the Prince Imperial in the Anglo-Zulu War on 1 June 1879. Queen Victoria's journal records their grief: "Dear Beatrice, crying very much as I did too, gave me the telegram ... It was dawning and little sleep did I get ... Beatrice is so distressed; everyone quite stunned."

The devotion that Beatrice showed to her mother was acknowledged in the Queen's letters and journals, but her constant need for Beatrice grew stronger. The Queen suffered another bereavement in 1883, when her highland servant, John Brown, died at Balmoral. Once again, the Queen plunged into public mourning and relied on Beatrice for support. Unlike her siblings, Beatrice had not shown dislike for Brown, and the two had often been seen in each other's company; indeed, they had worked together to carry out the Queen's wishes.

Beatrice and Henry were married at Saint Mildred's Church at Whippingham, near Osborne, on 23 July 1885. Beatrice, who wore her mother's wedding veil of Honiton lace, was escorted by the Queen and Beatrice's eldest brother, the Prince of Wales. Princess Beatrice was attended by ten royal bridesmaids from among her nieces: Princess Alix and Princess Irene of Hesse and by Rhine; Princess Alexandra, Princess Marie, and Princess Victoria Melita of Edinburgh; Princess Louise, Princess Maud, and Princess Victoria of Wales; Princess Marie Louise and Princess Helena Victoria of Schleswig-Holstein. The bridegroom's supporters were his brothers, Prince Alexander of Bulgaria and Prince Francis Joseph of Battenberg.

In 1886, when she agreed to open the Show of the Royal Horticultural Society of Southampton, the organisers sent her a proclamation of thanks, expressing their "admiration of the affectionate manner in which you have comforted and assisted your widowed mother our Gracious Sovereign the Queen". As a wedding present, Sir Moses Montefiore, a banker and philanthropist, presented Beatrice and Henry with a silver tea Service inscribed: "Many daughters have acted virtuously, but thou excellest them all." The Times newspaper, shortly before Beatrice's marriage, wrote: "The devotion of your Royal Highness to our beloved Sovereign has won our warmest admiration and our deepest gratitude. May those blessings which it has hitherto been your constant aim to confer on others now be returned in full measure to yourself." The sentence was, as far as it dared, criticising the Queen's hold over her daughter.

Although court entertainments were few after the Prince Consort's death, Beatrice and the Queen enjoyed tableau vivant photography, which was often performed at the royal residences. Henry, increasingly bored by the lack of activity at court, longed for employment, and in response, the Queen made him Governor of the Isle of Wight in 1889. However, he yearned for military adventure and pleaded with his mother-in-law to let him join the Ashanti expedition fighting in the Anglo-Asante war. Despite misgivings, the Queen consented, and Henry and Beatrice parted on 6 December 1895; they would not meet again. Henry contracted malaria and was sent home. On 22 January 1896, Beatrice, who was waiting for her husband at Madeira, received a telegram informing her of Henry's death two days earlier.

Princess Beatrice, who was Governor of the Isle of Wight from 1896 until her death in 1944, was also President of the Frank James Memorial Hospital at East Cowes, from 1903 until her death.

Beatrice's life was overturned by the death of Queen Victoria on 22 January 1901. She wrote to the Principal of the University of Glasgow in March, "... you may imagine what the grief is. I, who had hardly ever been separated from my dear mother, can hardly realise what life will be like without her, who was the centre of everything." Beatrice's public appearances continued, but her position at court was diminished. She, unlike her sister Louise, was not close to her brother, now King Edward VII, and was not included in the King's inner circle. Although their relationship did not break down completely, it was occasionally strained, for Example when she accidentally (but noisily) dropped her Service book from the royal gallery onto a table of gold plate during his coronation.

The beauty of Beatrice's daughter, Ena, was known throughout Europe, and, despite her low rank, she was a desirable bride. Her chosen suitor was King Alfonso XIII of Spain. However, the marriage caused controversy in Britain, since it required Ena to convert to Catholicism. This step was opposed by Beatrice's brother, King Edward VII, and Spanish ultra-conservatives were against the King's marriage to a Protestant of low birth, as her father, Prince Henry, was the son of a morganatic marriage. Thus, they considered Ena to be only partly royal and thus unfit to be Queen of Spain. Nonetheless, the couple wed on 31 May 1906. The marriage began inauspiciously when an anarchist attempted to bomb them on their wedding day. Apparently close at first, the couple grew apart. Ena became unpopular in Spain and grew more so when it was discovered that her son, the heir to the throne, suffered from haemophilia, a disease for which Alfonso held Beatrice responsible for having brought the disease to the Spanish royal house and turned bitterly against Ena.

Some of the buildings with which Beatrice would have been familiar, continue to be regularly used by the royal family: Buckingham Palace, Windsor Castle, Balmoral Castle, and Kensington Palace. She died at Brantridge Park, the home of her niece, Princess Alice, and her husband, the Earl of Athlone, at the time serving as Governor General of Canada. Osborne House, her mother's favourite home, is accessible to the public. Her Osborne residences, Osborne and Albert Cottages, remain in private ownership after their sale in 1912. At her death, Beatrice was the only surviving child of Queen Victoria and Prince Albert. The Future Elizabeth II, Beatrice's great-grandniece, was eighteen years of age at that time.

During her time as Queen of Spain, Ena returned many times to visit her mother in Britain, but always without Alfonso and usually without her children. Meanwhile, Beatrice lived at Osborne Cottage in East Cowes until she sold it in 1913, when Carisbrooke Castle, home of the Governor of the Isle of Wight, became vacant. She moved into the Castle while keeping an apartment at Kensington Palace in London. She had been much involved in collecting material for the Carisbrooke Castle museum, which she opened in 1898.

Her presence at court further decreased as she aged. Devastated by the death of her favourite son, Maurice, during the First World War in 1914, she began to retire from public life. In response to war with Germany, George V changed the name of the royal house from Saxe-Coburg and Gotha to Windsor and at the same time adopted it as the family surname, to downplay their German origins. Subsequently, Beatrice and her family renounced their German titles; Beatrice's style reverted from HRH Princess Henry of Battenberg to her birth style, HRH The Princess Beatrice. She adopted the surname of Mountbatten. Her sons gave up their style, Prince of Battenberg. Alexander, the eldest, became Sir Alexander Mountbatten and was later given the title Marquess of Carisbrooke in the Peerage of the United Kingdom. Her younger son, Leopold, became Lord Leopold Mountbatten and was given the rank of a younger son of a marquess. He was a haemophiliac, having inherited the "royal disease" from his mother, and died during a knee operation in 1922 one month short of his 33rd birthday.

Beatrice was the shyest of all of Queen Victoria's children. However, because she accompanied Queen Victoria almost wherever she went, she became among the best known. Despite her shyness, she was an able Actress and Dancer as well as a keen Artist and Photographer. She was devoted to her children and was concerned when they misbehaved at school. To those who enjoyed her friendship, she was loyal and had a sense of humour, and as a public figure she was driven by a strong sense of duty. She was Patron of the Isle of Wight Branch of the Royal National Lifeboat Institution from 1920 until her death. Music, a passion that was shared by her mother and the Prince Consort, was something in which Beatrice excelled, and she played the piano to professional standards. Like her mother, she was a devout Christian, fascinated by theology until her death. With her calm temperament and personal warmth, the Princess won wide approval.

Following the war, Beatrice was one of several members of the royal family who became patrons of The Ypres League, a society founded for veterans of the Ypres Salient and bereaved relatives of those killed in fighting in the Salient. She was herself a bereaved mother, as her son, Prince Maurice of Battenberg, had been killed in action during the First Battle of Ypres. Rare public appearances after his death included commemorations, including laying wreaths at the Cenotaph in 1930 and 1935 to mark the 10th and 15th anniversaries of the founding of the League.

Queen Victoria had given Beatrice the task of editing the journals for publication, which meant removing private material as well as passages that, if published, might be hurtful to living people. Beatrice deleted so much material that the edited journals are only a third as long as the originals. The destruction of such large passages of Queen Victoria's diaries distressed Beatrice's nephew, King George V, and his wife Queen Mary, who were powerless to intervene. Beatrice copied a draft from the original and then copied her draft into a set of blue notebooks. Both the originals and her first drafts were destroyed as she progressed. The task took thirty years and was finished in 1931. The surviving 111 notebooks are kept in the Royal Archives at Windsor Castle.

Even in her seventies, Beatrice continued to correspond with her friends and relatives and to make rare public appearances, such as when, pushed in a wheelchair, she viewed the wreaths laid after the death of George V in 1936. She published her last work of translation in 1941. Entitled "In Napoleonic Days", it was the personal diary of Queen Victoria's maternal grandmother, Augusta, Duchess of Saxe-Coburg-Saalfeld. She corresponded with the publisher, John Murray, who greatly approved of the work. She made her last home at Brantridge Park in West Sussex, which was owned by Queen Mary's brother, Alexander Cambridge, the first Earl of Athlone, and his wife, Princess Alice, who was Beatrice's niece; the Athlones were at the time in Canada where the Earl was Governor-General. There, Beatrice died in her sleep on 26 October 1944, aged eighty-seven (the day before the 30th anniversary of her son, Prince Maurice's death). After her funeral Service in St George's Chapel, Windsor Castle, her coffin was placed in the royal vault on 3 November. On 28 August 1945, her body was transferred and placed inside a joint tomb, alongside her husband, in St. Mildred's Church, Whippingham. Beatrice's final wish, to be buried with her husband on the island most familiar to her, was fulfilled in a private Service at Whippingham attended only by her son, the Marquess of Carisbrooke, and his wife.

The ceremony – which was not attended by her eldest sister and brother-in-law, the Crown Prince and Princess of Prussia, who were detained in Germany; william Ewart Gladstone; or Beatrice's cousin, Princess Mary Adelaide, Duchess of Teck, who was in mourning for her father-in-law – ended with the couple's departure for their honeymoon at Quarr Abbey House, a few miles from Osborne. The Queen, taking leave of them, "bore up bravely till the departure and then fairly gave way", as she later admitted to the Crown Princess.

The depth of the Queen's grief over the death of her husband surprised her family, courtiers, politicians and general populace. As when her mother died, she shut herself off from her family—most particularly, the Prince of Wales, (whom she blamed for her husband's death), with the exception of Alice and Beatrice. Queen Victoria often took Beatrice from her cot, hurried to her bed and "lay there sleepless, clasping to her child, wrapped in the nightclothes of a man who would wear them no more." After 1871, when the last of Beatrice's elder sisters married, Queen Victoria came to rely upon her youngest daughter, who had declared from an early age: "I don't like weddings at all. I shall never be married. I shall stay with my mother." As her mother's secretary, she performed duties such as writing on the Queen's behalf and helping with political correspondence. These mundane duties mirrored those that had been performed in succession by her sisters, Alice, Helena and Louise. However, to these the Queen soon added more personal tasks. During a serious illness in 1871, the Queen dictated her journal entries to Beatrice, and in 1876 she allowed Beatrice to sort the music she and the Prince Consort had played, unused since his death fifteen years earlier.