Powys (/ˈpoʊɪs, ˈpaʊɪs/ POH-iss, POW-iss, Welsh: [ˈpou̯ɪs]) is a county and preserved county in Wales. It borders Gwynedd, Denbighshire, and Wrexham to the north; the English ceremonial counties of Shropshire and Herefordshire to the east; Monmouthshire, Blaenau Gwent, Merthyr Tydfil, Caerphilly, Rhondda Cynon Taf, and Neath Port Talbot to the south; and Carmarthenshire and Ceredigion to the west. The largest settlement is Newtown, and the administrative centre is Llandrindod Wells.

Powys is the largest and most sparsely populated county in Wales, having an area of 5,181 km (2,000 sq mi) and a population of 133,891 in 2022. After Newtown (11,362), the most populous settlements are Ystradgynlais (8,270), Brecon (8,254), and Llandrindod Wells (5,602). The county is entirely rural, and characterised by multiple market towns and villages. The Welsh language can be spoken by 16.4% of the population.

The county is predominantly hilly and mountainous. To the west lie the Cambrian Mountains, where the River Severn and River Wye both have their source on the Powys side of the Plynlimon massif; together with their tributaries they drain most of the county. The southern quarter of the county is occupied by the Brecon Beacons (Bannau Brycheiniog) national park, and further north are two more upland areas, Mynydd Epynt and Radnor Forest. The only extensive area of flat land in Powys is the region northwest of Welshpool.

The county is named after the Kingdom of Powys, which was a Welsh successor state, petty kingdom and principality that emerged during the Middle Ages following the end of Roman rule in Britain. Powys covers the same area as the historic counties of Montgomeryshire, Radnorshire, and Brecknockshire.

Powys covers the historic counties of Montgomeryshire and Radnorshire, most of Brecknockshire, and part of historic Denbighshire. With an area of about 2,000 square miles (5,200 km), it is now the largest administrative area in Wales by land and area (Dyfed was until 1996 before several former counties created by the Local Government Act 1972 were abolished). It is bounded to the north by Gwynedd, Denbighshire and Wrexham County Borough; to the west by Ceredigion and Carmarthenshire; to the east by Shropshire and Herefordshire; and to the south by Rhondda Cynon Taf, Merthyr Tydfil County Borough, Caerphilly County Borough, Blaenau Gwent, Monmouthshire and Neath Port Talbot.

The largest towns are Newtown, Ystradgynlais, Brecon, Welshpool, Llandrindod Wells and Knighton. Powys has the lowest population density of all the principal areas of Wales. Most of Powys is mountainous, and most roads and railways are relatively slow.

Just under a third of the residents have Welsh linguistic skills: 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, and the industrial area of Ystradgynlais in the southwest of Brecknockshire. In Radnorshire, the language survived into the 20th century west of Rhayader with a few native speakers from Nantmel parish surviving into the 20th century too. The 2021 census recorded that 16.4% of the population were able to speak the Welsh language, a decline from 18.6% in 2011 and 21% in 2001.

The county is named after the ancient Welsh Kingdom of Powys, which in the sixth century AD included the northern two-thirds of the area as well as most of Shropshire and adjacent areas now in England, and came to an end when it was occupied by Llywelyn ap Gruffudd of Gwynedd during the 1260s.

The uplands retain evidence of occupation from long before the Kingdom of Powys, and before the Romans, who built roads and forts across the area. There are 1130 identified burial mounds within the county, of varying styles and ages, dating from 4000 BC to 1000 BC, most of them belonging to the Bronze Age. Of these, 339 are scheduled monuments. Standing stones, most again dating to the Bronze Age, also occur in large numbers, 276 being found across the county, of which 92 are scheduled. From the Iron Age, the county has 90 scheduled hillforts and a further 54 enclosures and settlement sites.

Powys is served by the Cambrian Line and Heart of Wales line which offer connections to major towns and cities such as Swansea, Wrexham, Shrewsbury, Birmingham, Wolverhampton, Manchester, Cardiff, Aberystwyth, London and Telford. The county used to be served by key railways such as the Mid-Wales Railway, Oswestry and Newtown Railway, Tanat Valley Light Railway, Llanfyllin Branch, Leominster and Kington Railway, Swansea Vale Railway and the Hereford, Hay and Brecon Railway, all of which offered connections to South Wales, Hereford, Oswestry, North Wales and West Wales but have all since closed.

The gold in the county coat of arms symbolises the wealth of the area. Black is for both mining and the Black Mountains. The fountain is a medieval heraldic charge displayed as a roundel barry wavy argent and azure. It represents water and refers to both the water catchment area and the rivers and lakes. Thus, the arms contain references to the hills and mountains, rivers and lakes, water supply and industry. The crest continues the colouring of the arms. A tower has been used in preference to a mural crown, which alludes to the county's military history and remains. From the tower rises a red kite, a bird almost extinct elsewhere in Britain but thriving in Powys. The bird is a "semé of black lozenges" for the former coal mining industry, while the golden fleece it carries is a reference to the importance of sheep rearing in the county.

The county motto is: Powys – the paradise of Wales (Welsh: Powys Paradwys Cymru).

On 1 April 1974, Powys was created under the Local Government Act 1972. At first, the former administrative counties of Montgomery, Radnor, and Brecknock were districts within it. On 1 April 1996, the districts were abolished, and Powys was reconstituted as a unitary authority. There was a minor border adjustment in the northeast—specifically, the addition of the communities of Llansilin and Llangedwyn from Glyndŵr district in Clwyd—and with moving the border, so that rather than half of Llanrhaeadr-ym-Mochnant, all is included.

The first Lord Lieutenant of Powys was previously the Lord Lieutenant of Montgomeryshire. The Lord Lieutenant of Brecknockshire and Lord Lieutenant of Radnorshire were appointed as lieutenants. The present lord lieutenant is Shân Legge-Bourke of Crickhowell.

From 2024, Powys would be in the UK parliament constituencies of Brecon, Radnor and Cwm Tawe and Montgomeryshire and Glyndŵr, both of which extend out of the county.

In December 2007, Powys was awarded Fair Trade County status by The Fairtrade Foundation.

• List of Lord Lieutenants of Powys
• List of High Sheriffs of Powys
• List of schools in Powys
• List of churches in Powys

• Powys Heritage
• Tourism in Powys