Lucas Malet (1852-1931) was an English novelist. Her real name was Mary St. Leger Kingsley Harrison.

Mary St Leger Kingsley was born on June 4, 1852 in Eversley, Hampshire, England, third of four children of social reformer Reverend Charles Kingsley and his wife Frances Eliza Grenfell. Mary studied under Sir Edward Poynter at the Slade School of Fine Art in the early 1870s. In 1876 she married Reverend William Harrison, her father's curate, and left behind her artistic career. Unfortunately the marriage was unhappy and childless; the couple soon amicably separated. Mary's began writing under the pseudonym Lucas Malet began at the end of the Victorian Age and carried through the Edwardian Age into the Modernist Period. Among her best known works are Colonel Enderby's Wife, The Wages of Sin, and The History of Sir Richard Calmady. Mary travelled extensively, living part of the year in Switzerland. She died in Tenby, Wales on October 27, 1931.