Born in 1717, Williams is often known simply as Pantycelyn, the name of the farm on which he lived most of his adult life.
A leading figure in the Welsh Methodist Revival of the 18th century, these days he is perhaps best remembered as the man who wrote the favourite hymn of all Welsh rugby supporters, Guide Me, O Thou Great Jehovah. Most know it as Bread Of Heaven.
Williams was the son of John Williams, a farmer who worked the land around Pantycelyn farm outside Llandovery in Carmarthenshire. The family worshipped as Calvinists and their doctrine of pre-destination was something to stay with Williams all his life.
He intended to become a doctor but, having heard Howell Harris preach at Talgarth in 1737, underwent an immediate conversion and became fired with religious conviction. In 1740 he was appointed curate to Theophilus Evans, in charge of several rural Welsh parishes, but was refused ordination as a priest because of his Methodist leanings.
Methodism was originally a movement within the Church of England, which included, in those days, all churches in Wales. Methodists never intended to break away from the Church of England, the purpose of the movement being to revive Christianity and worship within the church and to give it new impetus. However, the Methodists aroused much animosity and hostility from church authorities and some members.
Unable to make a living as a priest, William Williams became an itinerant preacher, travelling hundreds of miles around Wales, usually giving his sermons in the open air - something else that was frowned upon by church authorities. Wherever he went he created dozens of local Methodist fellowships, right across the country, so that his supporters could continue to meet and worship together after he had moved on.
Despite being a great preacher and organiser, it is as a hymn writer and poet that William Williams, Pantycelyn, is best remembered. In all he produced nearly 1,000 hymns, most of them in his native Welsh but some in English. His first hymn book was published in 1744, and the people of Wales quickly took it to their hearts. They loved the wonderful cadences of his verses, and many of the hymns are still sung today.
Y Per Ganiedydd or sweet singer
Williams is sometimes known as Y Per Ganiedydd, which in English translates as "sweet singer". He was also an accomplished prose writer, producing numerous theological treatises and elegies on people such as Griffith Jones of Llandowror, a clergyman who was not a Methodist but who had definite sympathies with the movement - and whose circulating schools helped to create a literate Welsh people.
William Williams, with his wonderful poetry and lyrical verses, also helped the Welsh language to remain strong, develop and grow. But it is as a religious figure of considerable substance and power that he really made his mark.
At the end of the 18th century, with the deaths of the three great Methodist leaders in Wales, the intense fervour of the Methodist Revival began to slowly slip away. However, it was not before the Calvinistic Methodists had become a clearly defined group. In many cases the small fellowship groups that had been created by people like Williams had already left the established churches to build their own places of worship.
In 1811 came secession from the Church of England and, 12 years later, the Calvinistic Methodist Presbyterian Church of Wales was established. Williams would perhaps not have wanted such a move but it was perhaps inevitable given the mood of church authorities and worshippers.
William Williams, Pantycelyn, died on 11 January 1791 and was buried in the churchyard at Llanfair-ar-y-bryn, just outside Llandovery. He remains one of the great figures of Welsh religion - indeed, one of the great figures of Welsh social history. Every year, when the Welsh rugby fans bawl out Bread Of Heaven, they are paying tribute to a remarkable and fascinating man.