Powys covers the historic counties of Montgomeryshire and Radnorshire, most of Brecknockshire, and a small part of Denbighshire, an area of 5,196 km squared, making it the largest county in Wales by land area. It is bounded to the north by Gwynedd, Denbighshire and Wrexham; to the west by Ceredigion and Carmarthenshire; to the east by Shropshire and Herefordshire; and to the south by Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Blaenau Gwent, Monmouthshire and Neath Port Talbot. Most of Powys is mountainous, with north-south transportation by car being difficult.

The majority of the Powys population is made up of small villages and towns. The largest is Newtown, with a population of 12,783 (2001).Just under a third of the residents have Welsh linguistic skills and Welsh speakers are concentrated mainly in the rural areas both in and around Machynlleth, Llanfyllin and Llanrhaeadr-ym-Mochnant (where William Morgan first translated the whole Bible into Welsh in 1588) in Montgomeryshire (Welsh: Sir Drefaldwyn), and the industrial area of Ystradgynlais in the extreme south-west of Brecknockshire (Welsh: Sir Frycheiniog). Radnorshire (Welsh: Sir Faesyfed) was almost completely Anglicised by the end of the 18th century.