Mary Ethel Florey (née Hayter Reed), Baroness Florey (1 October 1900 – 10 October 1966) was an Australian doctor and medical scientist. Her work was instrumental in the discovery of penicillin. She was part of the team that ran the first trials on penicillin and first administered the drug in a human trial. Part of her research has been summarized in a four volume book on antibiotics published from 1952 to 1960.