Dame Agatha Mary Clarissa Christie, Lady Mallowan, (née Miller; 15 September 1890 – 12 January 1976) was an English writer known for her 66 detective novels and 14 short story collections, particularly those revolving around fictional detectives Hercule Poirot and Miss Marple. She also wrote the world's longest-running play, the murder mystery The Mousetrap, which has been performed in the West End of London since 1952. A writer during the "Golden Age of Detective Fiction", Christie has been called the "Queen of Crime"—a moniker which is now trademarked by her estate—or the "Queen of Mystery". She also wrote six novels under the pseudonym Mary Westmacott. In 1971, she was made a Dame (DBE) by Queen Elizabeth II for her contributions to literature. Guinness World Records lists Christie as the best-selling fiction writer of all time, her novels having sold more than two billion copies.

Christie was born into a wealthy upper-middle-class family in Torquay, Devon, and was largely home-schooled. She was initially an unsuccessful writer with six consecutive rejections, but this changed in 1920 when The Mysterious Affair at Styles, featuring detective Hercule Poirot, was published. Her first husband was Archibald Christie; they married in 1914 and had one child before divorcing in 1928. Following the breakdown of her marriage and the death of her mother in 1926, she made international headlines by going missing for eleven days.