Mass rock

A Mass rock (Irish: Carraig an Aifrinn) was a rock used as an altar by the Catholic Church in Ireland, during the 17th and 18th centuries, as a location for secret and illegal gatherings of faithful attending the Mass offered by outlawed priests. Similar altars, known as Mass stones, were used by the similarly illegal and underground Catholic Church in Scotland, membership in which was similarly criminalised following the Scottish Reformation in the mid-16th century.

During the religious persecution of the Catholic Church in Ireland isolated locations were sought to hold religious ceremonies, as observing the Catholic Mass was a matter of difficulty and danger at the time as a result of the Reformation in Ireland, Cromwell's campaign against the Irish, and the Penal Laws of 1695. Bishops were banished and priests had to register to preach under the 1704 Registration Act. Priest hunters were employed to arrest Catholic priests and nonjuring Vicars of the Scottish Episcopal Church under an Act of 1709.