The Franciscan Brothers of Brooklyn, formally known as the Congregation of the Religious Brothers of the Third Order Regular of St. Francis, were founded in Brooklyn, New York, in 1858. They have been actively involved in the education of boys and young men, primarily on Long Island, New York, serving the Diocese of Brooklyn (and later also the Diocese of Rockville Centre) since their founding. The Brothers of the congregation use the postnominal initials of O.S.F.. Numbering 80 members as of 2008, they are the largest congregation of Religious Brothers founded in the America.
Ireland had been the home of 47 monasteries of friars, both priests and laybrothers, of the Franciscan Third Order Regular, which were centers of learning. These communities were suppressed under the Penal Laws put in place in their land under English rule, of which only Rosserk Friary in County Mayo has survived to modern times. The Order continued in hiding, with only lay members. Their ministry was that of instructing Catholic boys in the faith in underground "bog schools".
After the ban on education by Catholics was repealed in 1782, two Brothers established themselves as the Franciscan Brothers of Ireland, a congregation of Religious Brothers, and opened a monastery and free primary school for poor boys in Milltown, Dublin. Several foundations soon followed. In 1818 they were given land in Mountbellew, County Galway, to which the monastery moved and opened a primary school, now the Mountbellew Agricultural College.