Mary Arnold may refer to:
Mary Arnold (tennis) (1916–1975), American tennis player Mary Anne Arnold (c. 1825–?), English sailor and crossdresser Mary Arnold (singer) (born 1947), American singer Mary Daisy Arnold (1873–1955), American botanical artist Mary Ellicott Arnold (1876–1968), American social activist, teacher and writer Mary Peterson Arnold (1885–1973), American politician Mary Augusta Ward (née Arnold; 1851–1920), British writer