[Latin]
One of the five principal tribes of pre-Roman and Roman Wales, according to the geographer Ptolemy (2nd cent. AD), occupying the south-western extremity of the country between the Rivers Teifi and Tywi, largely coextensive with the territory later known as Dyfed. The Demetae appear to have offered little resistance to the Romans, and their homeland, known as Demetia, became a region of settled pastoralism. At the end of the 4th cent. AD Demetia was invaded by the Déisi from Ireland. Dewi Sant, patron saint of Wales, directed his main missionary activity towards portions of Demetia. The numerically superior Demetae eventually absorbed the Déisi.