Phil Williams was born in Tredegar but grew up in Bargoed where he went to Lewis School Pengam and then on leaving school he went to University of Cambridge, upon leaving he became a leading space scientist and was appointed a Professor of Solar Terrestrial Physics at the University College of Wales in Aberystwyth around the same time he became the economic spokesman for the political party Plaid Cymru.

In 1968 he stood as the candidate of Caerphilly by-election and became the first Chairman of Plaid Cymru in 1970, which was the post he held until 1976; when he became Vice President of the party. He was responsible for policy and research in the party for many years.

From 1999 to 2003, Later his political he was became a member of the National Assembly for Wales for the electoral region of South Wales East. In 1999 he stood for Blaenau Gwent and recieved 21% of the vote.

During 2001 he was voted Welsh Politician of the Year, and he was being pressured by former colleagues to become the next president of his party, following the resignation of Ieuan Wyn Jones as president.

In 2003 he stood down as an Assembly and started working on a research project to study the inner workings of the sun from the observatory near the North Pole. In 2001, but shortly after standing down from the Welsh Assembly he suffered a heart attack while visiting the "A Touch of Class" a massage parlour and brothel situated in Cardif and was taken to the University Hospital of Wales where he was pronounced dead.