Mary May Scollen was born on May 11, 1887 in Redfern, Sydney, New South Wales, Australia, second child in the family. Her parents, Patrick Scollen (a laborer turned contractor) and Susan Smith, had emigrated from Ireland.
In 1905, Mary May entered the Sisters of Mercy convent in North Sydney, a suburb of Sydney. This order, founded by an Irish heiress, Catherine McAuley, was dedicated to teaching and caring for the sick. In religious life, she was known as Sr. Mary Justinian. She professed vows on December 26, 1907.
As a new religious, Sr. Justinian studied nursing at Mater Hospital and passed her qualifying exams to become a professional nurse in 1911. After serving in the hospital a clinical nurse, in 1919 she was appointed matron of the hospital. In this role, she was in charge of overseeing all clinical nursing and nursing education.
One of the first challenges she faced was coping with a Spanish flu pandemic. Her hospital devoted one whole ward to caring for such patients, and by the time the flu had passed, the hospital had treated 262 Spanish flu patients. Because of excellent nursing care, the vast majority of the Spanish flu patients survived.
Although Sr. Justinian was a good clinician and administrator, she also had a passion for nursing education. Therefore, in 1955, Sr. Justinian helped found the New South Wales College of Nursing.
The British government honored Sr. Justinian for her outstanding contributions to the field of nursing by making her a member of the Order of the British Empire (M.B.E.) on January 1, 1958.
In 1963, after 44 years as hospital matron, Sr. Justinian became Mother Justinian when she was named the superior of the North Sydney convent of the Sisters of Mercy and administrator of Mater Hospital. She served a four-year term but retired in 1967 because of ill health.
Mother Justinian died on October 22, 1967 in the same hospital where she had trained and practiced nursing for so many years.