William Price (4 March 1800 – 23 January 1893) was a Welsh medical doctor and socio-political activist known for his support of Welsh nationalism, Chartism, and his involvement with the Neo-Druidic religious movement. He has been recognized as one of the most significant figures of 19th-century Wales, and one of the most unusual in Victorian Britain.Born to a lower-class household in Glamorganshire, Wales, Price trained as a doctor in London before returning to Wales, becoming interested in the Chartists' ideas regarding equal democratic rights for all men. Following their failed 1839 uprising, he escaped government prosecution by fleeing to France, where he became convinced that an ancient prophecy predicted that he would remove Wales from English rule.

Returning to Wales, Price tried reviving what he believed to be the religion of the ancient druids, the Celtic Iron Age ritual specialists of Western Europe. In doing so, he became one of the most prominent proponents of the Neo-Druidic movement, something that had been developing since Iolo Morganwg's activities in the late 18th century. After cremating his dead son in 1884, Price was arrested and put on trial by those who believed cremation was illegal in the United Kingdom; however, he successfully argued that there was no legislation that specifically outlawed it, which paved the way for the Cremation Act 1902. Upon his death, he was cremated in a ceremony watched by 20,000 onlookers.

Known for adhering to such principles as equal democratic rights for all men, anti-vaccinationism, anti-vivisectionism, vegetarianism, cremation, and the abolition of marriage, some of which were highly controversial at the time, he has been widely known as an "eccentric" and a "radical". A permanent exhibition and statue dedicated to him being was opened by these people in the town of Llantrisant, where he had lived for much of his later life.