Ystalyfera is a former industrial village and community in the upper Swansea Valley, on the River Tawe, about 13 miles (21 km) northeast of Swansea. It is an electoral ward and a community in the unitary authority of Neath Port Talbot, Wales, comprising a resident population of just over 3,000 people, approximately 60% of whom speak Welsh.

The River Tawe is a 30 miles (48 km) long river in South Wales. Its headwaters flow initially east from its source below Llyn y Fan Fawr south of Moel Feity in the Black Mountains, the westernmost range of the Brecon Beacons National Park, before the river turns south and then southwest to its estuary at Swansea. Its main tributaries are the right bank Upper and Lower Clydach Rivers and the Afon Twrch. The total area of the catchment is some 246 km2 (95 sq mi). The Tawe passes through a number of towns and villages including Ystradgynlais, Ystalyfera, Pontardawe, and Clydach and meets the sea at Swansea Bay below Swansea. The Tawe Valley is more commonly known as the Swansea Valley.