Mary McLean Loughron was born in Winchelsea, Victoria. She trained as a nurse at the Royal Melbourne Hospital before deciding to join the war effort, embarking with an Australian medical group on the RMS Orontes in early 1915. After arriving in France, Loughron enlisted with the British Army, joining the Queen Alexandra's Imperial Military Nursing Service (QAIMNS), and was eventually stationed at 2nd Stationary Hospital Annexe in Abbeville.

During her service, Loughron was twice awarded the Royal Red Cross (RRC), one Second and one First Class, and was Mentioned in Despatches on 30 April 1916 for gallant and distinguished conduct in the field. She served in France until the end of the First World War, and immediately afterwards worked as Matron of the Peace Conference Hospital in Paris. A portrait of Matron Loughron dressed in the indoor uniform of the QAIMNS was hung in the gallery of Portraits of the Allies in the Luxembourg, to represent the British Army Nursing Service.

Loughron returned to Australia on the SS Orvieto in December of 1919. She went on to open a private hospital in Camberwell, Victoria, which she operated for 10 years, and later spent 20 years as chief inspector for Victoria for the Child Welfare Department.