Margaret Kennedy was born in London on 23 April 1896, the eldest of four children. She attended Cheltenham Ladies' College, then went on to study history at Somerville College, Oxford. Her first book, a commissioned work of history, was published in 1922 and was soon followed by her first work of fiction, The Ladies of Lyndon (1923). Her second novel, The Constant Nymph (1924), became a worldwide bestseller, and with it Kennedy became a well-known and highly praised writer. The following year she married David Davies, a barrister; they lived in London and had three children. Kennedy went on to write fifteen further novels, many of which were critically commended - Troy Chimneys (1953) was awarded the James Tait Black Memorial Prize. She also wrote plays, adapting both The Constant Nymph and its sequel The Fool of the Family very successfully. The former opened in the West End in 1926, starring Noel Coward followed by John Gielgud, to great acclaim. Three different film versions of The Constant Nymph, featuring stars of the time such as Ivor Novello and Joan Fontaine, were equally popular, and led to Kennedy's engagement in film work for a number of years from the late 1930s. She also published a study of Jane Austen (1950) and a work of literary criticism, The Outlaws on Parnassus, in 1958. In 1964 Margaret Kennedy moved from London to Woodstock, Oxfordshire, where she lived until her death on 31 July 1967.