John Davies is a native of the Rhondda. He was educated in schools in Treorci, Bwlchllan and Tregaron and at University College, Cardiff, and Trinity College, Cambridge.
He taught at the University Colleges of Swansea and Aberystwyth and was for eighteen years the Warden of Neuadd Pantycelyn, Aberystwyth.
His publications include Cardiff and the Marquesses of Bute, Hanes Cymru, A History of Wales, Broadcasting and the BBC in Wales, The Making of Wales, The Celts and Cardiff: a Pocket Guide.
He was the consultant editor and a co-editor of The Encyclopaedia of Wales/Gwyddoniadur Cymru. In 1997, he was the keynote speaker at the inaugural meeting of the North American Association for the Study of Welsh History and Culture. He has broadcasted extensively, especially on historical subjects.