Charlotte Armstrong Lewi (May 2, 1905 in Vulcan, Michigan – July 7, 1969 in Glendale, California) was an American author. Under the names Charlotte Armstrong and Jo Valentine she wrote 29 novels. She also worked for The New York Times' advertising department, as a fashion reporter for Breath of the Avenue (a buyer's guide), and in an accounting firm.
Armstrong Lewi graduated from Vulcan High School in Vulcan, Michigan, in June 1921. She attended the junior college program at Ferry Hall in Lake Forest, Illinois for one year (1921–22), during which time she served as Editor-in-Chief of the student publication, Ferry Tales. She attended the University of Wisconsin–Madison and received a Bachelor of Arts degree from Barnard College in 1925. She had a daughter and two sons with her husband, Jack Lewi.
In 1957, she received an Edgar Award from the Mystery Writers of America for her novel A Dram of Poison. She wrote two other Edgar-nominated novels: The Gift Shop (1966) and Lemon in the Basket (1967). Three of her short stories, all published in Ellery Queen's Mystery Magazine, were nominated for Edgars: “And Already Lost” (1957), “The Case for Miss Peacock” (1965), and “The Splintered Monday” (1966).