The Princess Margaret, Countess of Snowdon (Margaret Rose; 21 August 1930 – 9 February 2002) was the younger sister of Queen Elizabeth II.

Margaret spent much of her early life in the company of her elder sister and parents, The Prince Albert, Duke of York (later King George VI) and Elizabeth, Duchess of York (later the Queen Mother). Her life changed dramatically in 1936, when her uncle, King Edward VIII, abdicated to marry the divorced American Wallis Simpson (later the Duke and Duchess of Windsor). Margaret's father became King in Edward's place, and after her sister, Elizabeth, Margaret became second in line to the throne.

During World War II, Margaret and Elizabeth stayed at Windsor Castle, despite government pressure to evacuate to Canada. During the war years, she was too young to partake in any public or official duties and instead continued her education. Among other things, she learned the piano and developed her singing voice. After the war, she fell in love with a divorced older man, Group Captain Peter Townsend, her father's equerry. Her father died at around the same time, and her older sister Elizabeth became Queen. Many in the government felt that Townsend was an unsuitable husband for the Queen's sister, and the Church of England refused to countenance the marriage. Under pressure, Margaret chose to abandon her plans, and instead accepted the proposal of the photographer Antony Armstrong-Jones, who was created Earl of Snowdon by the Queen. The marriage, despite an auspicious start, soon became unhappy; the couple divorced in 1978.