Knock is a village in County Mayo, Ireland. Knock is also a civil parish in the ancient barony of Costello. It is notable as the location of Knock Shrine- a Marian shrine and place of pilgrimage. According to Catholic beliefs, Mary, mother of Jesus, Saint Joseph and Saint John the Evangelist appeared to witnesses in the village on 21 August 1879. There is international skepticism of this event due to the age of the witnesses and the lack of evidence supporting the event.