Agatha Christie was a writer.
Dame Agatha Mary Clarissa Christie , Lady Mallowan , DBE ( née Miller ; 15 September 1890 -- 12 January 1976 ) was an English crime novelist , short story writer and playwright . She also wrote the world 's longest-running play , a murder mystery , The Mousetrap , and six romances under the name Mary Westmacott . Guinness World Records lists Christie as the best-selling novelist of all time .