Mary Ann Lyth (née , Hardy; after marriage, Mrs. R. B. Lyth; 1811 – September 1890) was a British missionary, translator, and teacher. She traveled to several countries with her husband, Rev. R. B. Lyth, M.D., the first Medical Missionary sent out by the Wesleyan Methodist Missionary Society, London. She provided basic European-style education at her various stations, and helped her husband as a nurse. She also assisted in the translation of the Bible, and other literary work.