Cynwyl Gaeo is an electoral ward, representing the communities of Cynwyl Gaeo, Llansawel and Llanycrwys, Carmarthenshire, Wales.
In 2014, the Cynwyl Gaeo electoral ward had an electorate of 1,323. The total population was 1,630, of whom 54.5% were born in Wales. The 2011 census indicated that 46.7% of the population were able to speak Welsh.
Cynwyl Gaeo is a single-member ward for the purposes of Carmarthenshire County Council elections. Since 1999 it has been represented by Plaid Cymru councillor Eirwyn Williams.