Mark Fraser Williams is a British politician who served as leader of the Welsh Liberal Democrats from 2016 to 2017. He was the Member of Parliament (MP) for the Ceredigion constituency, between 2005 and 2017. He sat on the Welsh Affairs Select Committee, and in 2006 he became a Shadow Minister for Wales under Menzies Campbell.

The Welsh Liberal Democrats are a branch of the United Kingdom Liberal Democrats that operates in Wales. The party is led by Jane Dodds, who served as MP for Brecon and Radnorshire from August to December 2019, and MS for Mid and West Wales since May 2021. The party currently has 1 elected member in the Senedd and no Welsh seats in the UK House of Commons, but does have several members of the House of Lords. The party had 69 local councilors serving in principal authorities as of the 2022 local authority elections, up 10 from 2017.