Abertillery (from Welsh Abertyleri, meaning "mouth of the River Tyleri", English pronunciation: æbərtɨˈlɛəri) is the largest town of the Ebbw Fach valley in what was the historic county of Monmouthshire, South Wales. Following local government reorganisation it became part of the Blaenau Gwent County Borough administrative area.The surrounding landscape borders the Brecon Beacons National Park and the Blaenavon World heritage Site.