Mary Catherine of St. Augustine (born Catherine de Simon de Longpré) was a 17th-century French nun who played a vital role in the early medical history of Quebec. Born in Saint-Sauveur-le-Vicomte, she joined the Augustinian order in 1644 before traveling to the colony of New France in 1648. During the voyage, she reportedly recovered from a plague. Once in Quebec, she dedicated her life to nursing the sick at the Hôtel-Dieu de Québec, serving as both a hospital treasurer and a novice mistress.