Brian Farrell L.C. (b. 8 February 1944) is a Catholic bishop and currently Secretary of the Pontifical Council for Promoting Christian Unity.
Bishop Farrell was born in Dublin, Ireland. He studied for the priesthood with the Legionaries of Christ and was ordained on 26 November 1969 at the Basilica of our Lady of Guadalupe in Rome. He joined the Legionaries of Christ in 1961, and obtained his licentiate in philosophy at the Pontifical Gregorian University and his licentiate in theology at the Pontifical University of Saint Thomas Aquinas. He was the novice director in the Legionary seminary in Orange, Connecticut, from 1970 to 1976, and in 1981 he earned a doctorate in dogmatic theology from the Pontifical Gregorian University. He worked for the Vatican’s Secretariat of State from 1981 to 2002.
He was named secretary of the Pontifical Council for Promoting Christian Unity and was appointed Titular Bishop of the titular see of Abitinae under Cardinal Walter Kasper by Pope John Paul II. He was consecrated on 6 January 2003 by Pope John Paul II; his principal co-consecrators were Archbishops Leonardo Sandri and Antonio Maria Vegliò. In 2003 Farrell writes an article for the catalogue "The Tension of Origin" for the exhibition of the Italian artist Giovanni Bonaldi has for years engaged in Jewish-Christian dialogue through artistic expression.
Bishop Farrell is the older brother of Kevin Farrell, currently Bishop of Dallas.
On 30 September 2010 Bishop Farrell was named among the counselors to Archbishop Velasio De Paolis, the Pontifical Delegate to the Congregation of the Legionaries of Christ. The others are Msgr. Mario Marchesi, Father Gianfranco Ghirlanda, SJ, Father Agostino Montan, SC. Archbishop De Paolis and the four counselors will assist him in fulfilling his duties in the reorganisation of the Mexican congregation. He also announced the apostolic visitor to Regnum Christi, the lay movement associated with the Legion. The visitor to Regnum Christi will be Archbishop Ricardo Blázquez Pérez of Valladolid