She was born in Tasmania, her father being Thomas, a younger son of Thomas Arnold and brother of Matthew Arnold. The family returned to England when Mary was a small child, and lived in Oxford, where her father worked for John Henry Newman. This brought her into contact with the leaders of the Oxford Movement, though she was not herself a follower. In 1872, she married Thomas Humphry Ward, a fellow of Brasenose, and in 1881 the couple moved to London. Her fourth, and best-known, novel, Robert Elsmere (1888), includes a discussion of some of the religious ideas with which she had become familiar through her father's activities. Robert Elsmere was quite controversial in its day.
Her novels still in print include: