Mary Christianna Lewis (née Milne; 17 December 1907 – 11 March 1988), known professionally as Christianna Brand, was a British crime writer and children's author born in British Malaya.

Christianna Brand was born Mary Christianna Milne (1907) in Malaya but spent most of her childhood in England and India.^[1] She had a number of different occupations, including model, dancer, shop assistant and governess.^[2] Brand also wrote under the pseudonyms Mary Ann Ashe, Annabel Jones, Mary Brand, Mary Roland, and China Thompson. Christianna Brand served as chair of the Crime Writers' Association from 1972 to 1973.^[3]

She married Roland Lewis. Mary Lewis died on 11 March 1988, aged 80. Her estate was valued at £96 417.^[4]

Her first novel, Death in High Heels, was written while Brand was working as a salesgirl, the idea stemming from her fantasies about doing away with an annoying co-worker. In 1941, one of her best-loved characters, Inspector Cockrill of the Kent County Police, made his debut in the book Heads You Lose. The character would go on to appear in seven of her novels. Green for Danger is Brand's most famous novel. The whodunit, set in a World War II hospital, was adapted for film by Eagle-Lion Films in 1946, starring Alastair Sim as the Inspector. She dropped the series in the late 1950s and concentrated on various other genres as well as short stories. She was nominated three times for Edgar Awards: for the short stories "Poison in the Cup" (EQMM, Feb. 1969) and "Twist for Twist" (EQMM, May 1967) and for a nonfiction work about a Scottish murder case, Heaven Knows Who (1960). She is the author of the children's series Nurse Matilda, which Emma Thompson adapted to film as Nanny McPhee (2005).

Her Inspector Cockrill short stories and a previously unpublished Cockrill stage play were collected as The Spotted Cat and Other Mysteries from Inspector Cockrill's Casebook, edited by Tony Medawar (2002).

She was the cousin of the illustrator Edward Ardizzone.^[5]