阿嘉莎·玛丽·克莱丽莎·克莉丝蒂女爵士，DBE（Dame Agatha Mary Clarissa Christie，又译阿加莎·克里斯蒂，1890年9月15日－1976年1月12日），另外又称马洛温爵士夫人（Lady Mallowan），是英国侦探小说作家。玛丽·维斯马科特（Mary Westmacott）则是她写浪漫爱情小说所用的笔名。

据金氏世界纪录统计，阿嘉莎·克莉丝蒂是人类史上最畅销的著书作家。而将所有形式的著作算入，只有圣经与威廉·莎士比亚的著作的总销售量在她之上。至今其著作曾翻译成超过103种语言，总销突破20亿本。 在法国，截至2003年，她一共卖出4,000万本法文版的著作，为法国书籍销量纪录保持者，远胜于第二位法国大文豪左拉的2,200万本。她是公认的「侦探小说之后」（Queen of Crime），对英国侦探小说的发展有很重要的影响和富争议的启发。

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 six romances under the name Mary Westmacott, but she is best known for the 66 detective novels and 14 short story collections that she wrote under her own name, most of which revolve around the investigative work of such characters as Hercule Poirot, Jane Marple, Parker Pyne, Harley Quin/Mr Satterthwaite and Tommy and Tuppence Beresford. She wrote the world's longest-running play, a murder mystery, The Mousetrap. In 1971 she was made a Dame for her contribution to literature.