Frances Evelyn "Daisy" Greville, Countess of Warwick (née Maynard; 10 December 1861 – 26 July 1938) was a British socialite and philanthropist. Although embedded in late-Victorian British high society, she was also a campaigning socialist, supporting many schemes to aid the less well-off in education, housing, employment, and pay, and was often known as the "Red Countess". She established colleges for the education of women in agriculture and market gardening, first in Reading, then in Studley. She established a needlework school and employment scheme in Essex as well as using her ancestral homes to host events and schemes for the benefit of her tenants and workers. Greville was a long-term confidante and mistress to the Prince of Wales, who later became King Edward VII.

She was said to be referenced in the popular music hall song "Daisy Bell", owing to her rather unorthodox conduct.

Born at 27 Berkeley Square, London, she was the elder of two daughters of Colonel Charles Maynard (1814 – 2 January 1865) and his second wife, Blanche FitzRoy (1839 – 8 December 1933). Frances would always be known as Daisy. The Maynards' younger daughter and Daisy's sister was named after her mother and was always known as Blanchie. Blanchie later married Lord Algernon Gordon-Lennox and was the mother of Ivy Cavendish-Bentinck, Duchess of Portland.

Blanche FitzRoy's paternal great-grandfather was former Prime Minister Augustus FitzRoy, 3rd Duke of Grafton. Her maternal grandmother, Emily Charlotte Ogilvie, was the youngest daughter of Lady Emily Lennox (one of the Lennox sisters) by her second marriage.

Charles Maynard was the son and heir apparent of Henry Maynard, 3rd Viscount Maynard. As Charles died five months before his father, it was Daisy who inherited the Maynard estates in 1865, including the ancestral home of Easton Lodge in Little Easton, Essex. Two years after her father's death, her mother married Lord Rosslyn, a favourite courtier of Queen Victoria. They had five children, Daisy's half-sisters including the noted Millicent Leveson-Gower, Duchess of Sutherland, Sybil Fane, Countess of Westmorland and Lady Angela Forbes.

Frances Maynard was considered a possible wife for Queen Victoria's youngest son, Prince Leopold (later Duke of Albany). The Queen desired this and used Lord Beaconsfield to influence the Maynard family to this end. However, the match fell through, and by mutual choice, in 1881 Frances married Francis Greville, Lord Brooke, the eldest son and heir of George Greville, 4th Earl of Warwick, although her parents did not initially approve.

Lord Brooke succeeded to the earldom in 1893, and the family moved to Warwick Castle. Daisy's first child, and probably the only one fathered by her husband, was Leopold Guy (1882–1928), who later became the sixth Earl of Warwick. Marjorie Blanche (1884–1964), born three years after the marriage, was Daisy's second child. Daisy, in a 1923 conversation with Basil Dean, the husband of Mercy, stated that Marjorie was fathered by Lord Charles Beresford. The third, Charles Algernon (1885–1887), died aged 16 months, and may also have been fathered by Charles Beresford.

Daisy's fourth child was a son, Maynard (1898–1960), and the fifth, a daughter, Mercy (1904–1968). These were fathered by Joseph Frederick (Joe) Laycock, a millionaire bachelor with whom Daisy was infatuated despite his faithlessness to her. Mercy was fathered by Laycock after he had married Katherine Mary (Kitty), the Marchioness of Downshire, on 14 November 1902, after she had been divorced by Arthur Hill, 6th Marquess of Downshire, citing adultery with Laycock.