St Illtyd is a hamlet near Aberbeeg, in southeast Wales, within the historic boundaries of Monmouthshire. It is situated on the mountain road between Pontypool and Abertillery in Blaenau Gwent. It rests at about 1200 feet above sea level. The Royal Mail postcode is NP13 2AY. It is located 1.26 miles (2.03 km) south of Abertillery and 10.56 miles (16.99 km) north of Newport. The B4471 runs near to the village. The population of the wider community including nearby Aberbeeg and Llanhilleth is 4,797.