Lady Margaret Sackville (24 December 1881 – 18 April 1963) was an English poet and children’s author.
Born at 60 Grosvenor Street, Mayfair, Lady Margaret was the youngest child of Reginald Windsor Sackville, 7th Earl De La Warr She was a second cousin of Vita Sackville-West.
She began to write poetry at an early age and at sixteen became a protegée of Wilfrid Scawen Blunt. With his encouragement, she had her early poems published in periodicals such as The English Review, the Englishwoman's Review, Country Life, The Nation, The Spectator and the Pall Mall Gazette. She published her first book of poems, Floral Symphony, in 1900. In 1910 she edited A Book of Verse by Living Women. In her introduction, she noted that poetry was one of the few arts in which women were allowed to engage without opposition and made a direct connection between women's social freedom and the freedom of the imagination.
When the Poetry Society was formed in 1912, Lady Margaret was made its first president. She had also been the first president of its predecessor, the Poetry Recital Society, formed in 1909. Joy Grant, in her biography of Harold Monro, writes that Lady Margaret "spoke well and to the point at the inauguration, hoping that the Society would 'never become facile and "popular", to turn to a merely trivial gathering of persons amiably interested in the same ideal'. Her half-expressed fears were unfortunately fulfilled: the direction in which the Society was heading soon became obvious — poetry was made an excuse for pleasant social exchanges, for irrelevant snobbery, for the disagreeable consequences of organised association."
She had a passionate 15-year love affair with Ramsay MacDonald, recorded in letters they wrote to each other between 1913 and 1929. MacDonald repeatedly proposed to her, but she declined to be his wife. His biographer David Marquand speculated that, although social considerations were a factor in her refusal, the main reason was that they were of different religions. Lady Margaret was Roman Catholic, while MacDonald was raised in the Presbyterian Church, later joining the Free Church of Scotland. Lady Margaret never married.