Mark Fraser Williams (born 24 March 1966) is a British Welsh Liberal Democrat politician and former Member of Parliament (MP) for the Ceredigion constituency, a seat he gained from Plaid Cymru in 2005 and then lost again to Ben Lake of Plaid Cymru in the 2017 General Election.
He sat on the Welsh Affairs Select Committee, and in 2006 he became a Shadow Minister for Wales under Menzies Campbell.
Mark Williams is a graduate of the University of Wales, Aberystwyth and the University of Plymouth, and was Deputy Headteacher of a school in Llangorse near Brecon before becoming an MP.