Abertillery (Welsh Abertyleri) is an urban district in the county of Monmouthshire, Wales, 16 miles north-west of Newport, originally on the Great Western Railway. Its population rose steeply during the period of mining development in the Rhondda valleys, being 10,846 in the 1891 census and 21,945 ten years later. It lies in the mountainous mining district of Monmouthshire and Glamorganshire, in the valley of the Ebbw Fach , and the population was traditionally employed in the numerous coalmines, ironworks and tinplate works, now mostly defunct. Farther up the same valley are the mining townships of Nantyglo and Blaina , which form another sizeable urban district.

Abertillery has a traditional-style town centre and several small schools. Today, its population numbers around 18,000. Noted for its unspoilt rural scenery, Abertillery neighbours with the small districts of Aberbeeg and Cwmtillery .

The town's name is pronounced with the emphasis on the penultimate syllable, ie. it rhymes with "Mary," as in a song made popular by Welsh entertainer Ryan Davies:

"Blodwen and Mary from Abertillery..."