Williams was born in Llanfachreth in Merionethshire in 1781 and was baptised at the local church. His mother was a Calvivnistic Methodist and his father an Anglican. He was the sixth child of seven and was reputed to have been bright and lively.
When 13 William attended a service held in a farmhouse. The sermon had a great effect on this young listener. He became interested in religious matters and he attended a Congregatioanl Church (Penrty Stryt) and at 15 became a member there. Like his father he became a carpenter and at 19 he began preaching. His pastor, William Jones, encouraged him and taught him to write. He went to school at Aberhafesp, near Newtown, for nine months.
In 1803 he went to the Academy in Wrexham, but did not do very well because he did not speak much English. However, because of his gift for preaching he had many invitations to be a minister. In October 1808 he bacame the minister at Wern and Harwd. He established churches in Rhos, Rwabon and Llangollen. His fame as a preacher spread throughout Wales and he became a prominent minister in his denomination.
In 1836 he moved to Liverpool, but due to family health problems and his own, he returned to Wern in the Autumn of 1839 and remained there until his death in March 1840.