Cynwyl Gaeo is a parish and community located in rural Carmarthenshire, Wales, near the boundary with Ceredigion, in the upper Cothi valley about halfway between Lampeter and Llandovery.

[1] It includes the villages of Caio (Caeo), Crug-y-bar, Cwrtycadno, Ffarmers and Pumsaint.

Historically it was part of the commote of Caeo, which in turn was part of Y Cantref Mawr ("The Great Hundred"), a division of Ystrad Tywi.

The parish church of St Cynwyl in the village of Caeo is a Grade II* listed building.

[3] The community is bordered by the communities of: Cilycwm; Llanwrda; Llansadwrn; Talley; Llansawel; Pencarreg; and Llanycrwys, all being in Carmarthenshire; and by Llanfair Clydogau and Llanddewi Brefi in Ceredigion.