(18 February 1868[1]–16 July 1941) was an Irish Jesuit priest and academic, born in Ballyvocogue, Cappagh, County Limerick.

In 1924, he joined the staff of the Jesuit Milltown Park Institute in Dublin as Professor of Church History, Lecturer in Sociology, and later, Spiritual Father.

Cahill's guidance, organised public meetings three or four times a year, published pamphlets on current topics and even attempted to produce a weekly paper to further its ideals.

Cahill's anti-mason message, delivered in the 1920s and 1930s, also served as an analysis and apologetic against Talmudic Judaism.

In his works he cites papal teaching which describes the Masons as enemies of the Catholic Church, and gives evidence that these same Masons are influenced and given guidance by Jews: The modern anti-Christian movement, which centres around Liberalism, owes much of its rapid progress to the secret society of the free masons...Freemasonry today is the enemy of the Church and every Catholic Government and Catholic institution in the world.