Legion of Mary is a lay Catholic association whose members are giving service to the Church, on a voluntary basis, all over the world. It was founded in Myra House, Francis Street, Dublin, Ireland, on 7 September, 1921.

Members of Legion of Mary participate in the life of the parish by taking part in works like Visitation of families, the sick and the lonely, Visitation of hospitals and prisons and serving the most afflicted and marginalized people,  helping with other parish activities. In these works they encourage the living of the faith on a deeper level and sharing the faith with others.

Membership to Legion of Mary is free and open to all practicing Catholics. In Uganda, it is found in all the 19 Dioceses.

The National body of Legion of Mary is Senatus of Uganda.