Cynog Glyndwr Dafis (born 1939) is a Welsh politician for Plaid Cymru. He is also Steward and Bailiff of the Manor of Northstead.

He was an MP from 1992 until 2000 then resigned, in order to spend more time in his role as a member of the National Assembly for Wales. In 2002 he announced he would step down from the Assembly at the 2003 elections, and did so despite leader Ieuan Wyn Jones asking him not to. In 2003, soon after the elections, he announced his candidacy for leadership of the party, but lost to Dafydd Iwan.