Christianity in Cornwall (Cornish: Kristonedh yn Kernow) began in the 4th or 5th century AD when Western Christianity was introduced into Cornwall along with the rest of Roman Britain. Over time it became the official religion, superseding previous Celtic and Roman practices. Early Christianity in Cornwall was spread largely by the saints, including Saint Piran, the patron of the county. Cornwall, like other parts of Britain, is sometimes associated with the distinct collection of practices known as Celtic Christianity but was always in communion with the wider Catholic Church. The Cornish saints are commemorated in legends, churches and placenames.
In contrast to Wales, which produced Bible translations into Welsh, the churches of Cornwall never produced a translation of the Bible in the Cornish language, which may have contributed to that language's demise. During the English Reformation, churches in Cornwall officially became affiliated with the Church of England. In 1549, the Prayer Book Rebellion caused the deaths of thousands of people from Devon and Cornwall. The Methodism of John Wesley proved to be very popular with the working classes in Cornwall in the 19th century. Methodist chapels became important social centres, with male voice choirs and other church-affiliated groups playing a central role in the social lives of working class Cornishmen. Methodism still plays a large part in the religious life of Cornwall today, although Cornwall has shared in the post-World War II decline in British religious feeling. In 1876 a separate Cornish diocese of the Church of England was established with the bishop's see at Truro.