Knock (An Cnocce, meaning hill in Irish) is a village in Ireland in County Mayo, Province of Connacht, on the west side of the island, about an hour's drive from Galway. Knock is now out of the Gaeltacht. Until the early 2000s, the name on road signs was Cnoc Mhuire or “Mary's Hill”.

Today Knock is one of the main Catholic pilgrimage centers in Ireland. Knock is considered the Irish Lourdes. On August 21, 1879, the Virgin Mary, Saint Joseph, Saint John the Evangelist and Jesus in the form of a lamb appeared on the south gable of Knocktown Church. 15 people of all ages have seen this scene. Mary did not convey any message there other than through the vision of the importance of the Eucharist. A personal pilgrimage by Pope John Paul II in 1979 inspired further devotion to the holy site. Teresa of Calcutta visited the holy place in June 1993 and is visited by 1.5 million pilgrims every year. The site is open year-round.