Marguerite Antonia Radclyffe Hall (12 August 1880 – 7 October 1943) was an English poet and author, best known for the novel The Well of Loneliness, a groundbreaking work in lesbian literature. In adulthood, Hall often went by the name John, rather than Marguerite.

In the drawing rooms of Edwardian society, Marguerite made a small name as a poet and librettist. In 1907, she met a middle-aged fashionable singer, Mrs. Mabel Batten, known as 'Ladye", who introduced her to influential people. Batten and Radclyffe Hall entered into a long-term relationship. But before Batten died in 1916, Radclyffe Hall, known in private as 'John', had taken up with the second love of her life, Una, Lady Troubridge, who gave up her own creative aspirations (she was the first English translator of the French novelist Colette) to manage the household which she shared with 'John' for 28 years. With Batten, Radclyffe Hall converted to Catholicism; in the company of Una, she pursued an interest in animals and spiritualism. In later life, Radclyffe Hall chased after a younger woman named Evguenia Souline, a White Russian refugee. She died from cancer of the colon in October 1943.
As Radclyffe Hall (no hyphen; prefixed neither by 'John' nor 'Marguerite'), she published a volume of stories, Miss Ogilvy Finds Herself (1934), which describes how British society utilised 'masculine' women during the First World War and then dropped them afterwards, and a total of seven novels. However, the novel on which Radclyffe Hall's reputation rests primarily is The Well of Loneliness (1928).
The novel was successfully prosecuted for obscenity when if first came out, and remained banned in Britain until 1948. Vilified as 'the bible of lesbianism' by fire-and-brimstone reactionaries. In the seventies, the halcyon days of radical feminism, it was hailed as the first portrayal of a 'butch' woman.