Who is Agatha Christie? Agatha Mary Clarissa, Lady Mallowan, DBE (15 September 1890 — 12 January 1976), also known as Dame Agatha Christie, was an English crime fiction writer. She also wrote romances under the name Mary Westmacott, but is chiefly remembered for her 66 detective novels. Her work with these novels, particularly featuring detectives Hercule Poirot or Miss Marple, have given her the title the `Queen of Crime` and made her one of the most important and innovative writers in the development of the genre.