Welsh petty kingdom in the southwest, based on the former Roman civitas of the Demetae (roughly modern Pembrokeshire and western Carmarthenshire); its royal line was founded by Irish (Déisi) settlers in the 5th century.
Continued as a Welsh kingdom under its Irish-descended dynasty through the early medieval period; merged into the larger kingdom of Deheubarth around 920, and later became the basis of Pembrokeshire after the Norman invasion of Wales.
General survey of the Brittonic-speaking peoples and post-Roman Welsh/'Old North' kingdoms, including Dyfed and Rheged.