(R.S.M.), Roman Catholic religious congregation founded in Dublin in 1831 by Catherine Elizabeth McAuley (McAuley, Catherine Elizabeth). By 1822 she had developed a program for instructing and training poor girls, distributing food and clothing to the needy, and performing other works of mercy. In 1827, assisted mainly by wealthy women attracted to the religious life, she opened a centre for charitable works on Baggot Street in Dublin. Although she had not intended to be a religious or to found a religious congregation, she acceded to the insistence of the Archbishop of Dublin that she embrace the religious life, and on Dec. 12, 1831, after 15 months of preparation, she and two companions pronounced the simple vows of poverty, chastity, and obedience. The growth and diffusion of the congregation throughout the English-speaking world was rapid. The congregation is not governed centrally, although in the course of time unions have been effected among groups of convents.

The Sisters of Mercy engage in a wide range of apostolic works, including education, the care of the sick in their homes and in hospitals, the care of the aged and of orphans, and other forms of social service. In the United States alone they operate a score of colleges and many high schools, grammar schools, and hospitals.