Williams was born in Llangoed on Anglesey, but lived most of his life in nearby Llanfairpwllgwyngyll.
His activism started when he campaigned against the refusal of Brewer Spinks, an employer in Blaenau Ffestiniog, to permit his staff to speak Welsh.
This inspired him to become a founder of Undeb y Gymraeg Fyw, and through this organisation was the main organiser of Sioe Gymraeg y Borth (the Welsh show for Menai Bridge using the colloquial form of its Welsh name).
He was a long-serving councillor on Gwynedd County Council, and was twice the party's candidate for Anglesey, at the 1970 and 1979 general elections.
He wrote a number of books, on history, the Welsh language, and also his autobiography.