The Legion of Mary (Latin: Legio Mariae, postnominal abbreviation L.O.M.) is an international association of members of the Catholic Church who serve it on a voluntary basis. It was founded in Dublin, as a Marian movement by the layman and civil servant Frank Duff.
Membership is open to those who belong to the Catholic Church and believe in its teaching. Its stated mission is for active members to serve God under the banner of Mary by the corporal and spiritual works of Mercy, as mentioned in Chapter 33 of the Legion of Mary Handbook. The main apostolate of the Legion is activities directed towards Catholics and non-Catholics encouraging them in their faith or inviting them to become Catholic. This is usually done by encouraging them in prayer, attending Mass and learning more about the Catholic faith. The members of the Legion are engaged primarily in the performance of spiritual works of mercy, rather than works of material aid.
The object of the Legion of Mary is the glory of God through the holiness of its members developed by prayer and active co-operation in Mary’s and the Church’s work. The unit of the Legion of Mary is called a praesidium, which holds a weekly meeting, where prayer is intermingled with reports and discussion. Persons who wish to join the Legion must apply for membership in a Praesidium. The Legion sees as its priority the spiritual and social welfare of each individual. The members participate in the life of the parish through visitation of families, the sick, both in their homes and in hospitals and through collaboration in every apostolic and missionary undertaking sponsored by the parish. Every legionary is required to carry out a weekly apostolic work in the spirit of faith and in union with Mary.
Drawing its inspiration from the True Devotion to Mary, as taught by St. Louis Marie de Montfort, and which had a profound influence on the Founder of the Legion, the Servant of God, Frank Duff, the Legion is at the disposal of the Bishops and Priests for use in the mission of the Church. While essentially a lay association, legionaries look for spiritual and apostolic formation to priests and religious, who, as Legion Spiritual Directors, hold an honored place in the Legion system. The Legion requires ecclesiastical approval to work in a diocese or parish. Loyalty to the Magisterium and to Ecclesiastical Authority is a basic legionary principle. The Legion aims to bring Mary to the world as the infallible means of winning the world to Jesus and legionary service is based on the doctrine of the Mystical Body of Christ so that in their fellow members and in those they serve, legionaries seek to have the Person of our Lord once again seen and served by Mary, his Mother.
The basic unit of the Legion is called a praesidium, which is normally based in a parish. A parish may have more than one praesidium. To be an active legionary it is necessary to apply for membership in a praesidium, which holds a weekly meeting and allocates a weekly apostolic task to the members, who generally work in pairs. After a successful period of probation, members are called to make the Legionary Promise (this is only applicable for members over 18 years) which is directed to the Holy Spirit. Realizing the necessity for a strong support of prayer, the Legion has Auxiliary members, who associate themselves with the Legion by undertaking a service of prayer in its name. The administration of the Legion is carried out through its various councils at local, regional and national level. The central council, the Concilium Legionis Mariae, meets monthly in Dublin.