Mary O'Connell (better known as Sister Anthony, S.C.) (1814 – December 8, 1897) was an Irish immigrant to the United States, who became a Roman Catholic Religious Sister. A Sister of Charity of Cincinnati, she served with distinction as a nurse on the front lines of the American Civil War. Her work with the wounded and in health care in general caused her to be known as "the angel of the battlefield" and "the Florence Nightingale of America." Her portrait hangs in the Smithsonian Institute in Washington, DC.