Croagh Patrick, nicknamed 'the Reek', is a mountain with a height of 764 m (2,507 ft) and an important site of pilgrimage in County Mayo, Ireland. The mountain has a pyramid-shaped peak and overlooks Clew Bay, rising above the village of Murrisk, several miles from Westport. It has long been seen as a holy mountain. It was the focus of a prehistoric ritual landscape, and later became associated with Saint Patrick, who is said to have spent forty days fasting on the summit. There has been a church on the summit since the 5th century; the current church dates to the early 20th century. Croagh Patrick is climbed by thousands of pilgrims every year on Reek Sunday, the last Sunday in July, a custom which goes back to at least the Middle Ages.

County Mayo is a county in Ireland. In the West of Ireland, in the province of Connacht, it is named after the village of Mayo, now generally known as Mayo Abbey. Mayo County Council is the local authority. The population was 137,231 at the 2022 census. The boundaries of the county, which was formed in 1585, reflect the Mac William Íochtar lordship at that time.