Abertillery was a county constituency centred on the town of Abertillery in Monmouthshire. It returned one Member of Parliament (MP) to the House of Commons of the Parliament of the United Kingdom, elected by the first past the post system of election. From 1950 up to 1970, it was the safest Labour seat in the United Kingdom.

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.