The Leavenworth Case (1878), subtitled A Lawyer's Story, is an American detective novel and the first novel by Anna Katharine Green. Set in New York City, it concerns the murder of a retired merchant, Horatio Leavenworth, in his New York mansion. The popular novel introduced the detective Ebenezer Gryce, and was influential in the development of the detective novel. In her autobiography, Agatha Christie cited it as an influence on her own fiction.

Anna Katharine Green (November 11, 1846 – April 11, 1935) was an American poet and novelist. She was one of the first writers of detective fiction in America and distinguished herself by writing well plotted, legally accurate stories.