Abertillery is a town and a community of the Ebbw Fach valley in the historic county of Monmouthshire, Wales. Following local government reorganisation it became part of the Blaenau Gwent County Borough administrative area.

Until 1974, Monmouthshire, also formerly known as the County of Monmouth, was an administrative county in the south-east of Wales, on the border with England, and later classed as one of the thirteen historic counties of Wales. Its area now corresponds approximately to the present principal areas of Monmouthshire, Blaenau Gwent, Newport and Torfaen, and those parts of Caerphilly and Cardiff east of the Rhymney River.