There are three constituencies covering Powys. They are all county constituencies (CCs) of the House of Commons of the Parliament of the United Kingdom

Parliament of the United Kingdom

The Parliament of the United Kingdom of Great Britain and Northern Ireland is the supreme legislative body in the United Kingdom, British Crown dependencies and British overseas territories, located in London...

 (Westminster

Palace of Westminster

The Palace of Westminster, also known as the Houses of Parliament or Westminster Palace, is the meeting place of the two houses of the Parliament of the United Kingdom—the House of Lords and the House of Commons...

), and are used also, since the 1999 Welsh Assembly election

Welsh Assembly election, 1999

The first National Assembly for Wales elections were held on 6 May 1999. The overall turnout of voters was 46.3%. Although the Welsh Labour Party were the biggest party, they did not gain enough seats to form a majority government and instead entered into coalition with the Liberal Democrats...

, for elections to the National Assembly for Wales

National Assembly for Wales

The National Assembly for Wales is a devolved assembly with power to make legislation in Wales. The Assembly comprises 60 members, who are known as Assembly Members, or AMs...

.

Powys

Powys

Powys is a local-government county and preserved county in Wales.-Geography:Powys covers the historic counties of Montgomeryshire and Radnorshire, most of Brecknockshire , and a small part of Denbighshire — an area of 5,179 km², making it the largest county in Wales by land area.It is...

 is one of the eight preserved counties

Preserved counties of Wales

The preserved counties of Wales are the current areas used in Wales for the ceremonial purposes of Lieutenancy and Shrievalty. They are based on the counties created by the Local Government Act 1972 and used for local government and other purposes between 1974 and 1996.-Usage:The Local Government ...

 of Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

, and has the name and boundaries of one of the 22 principal areas.

One of the constituencies

United Kingdom constituencies

In the United Kingdom , each of the electoral areas or divisions called constituencies elects one or more members to a parliament or assembly.Within the United Kingdom there are now five bodies with members elected by constituencies:...

 straddles the boundary with another preserved county, and Boundary Commission for Wales proposals for new boundaries have been accepted, to become effective for the 2010 United Kingdom general election and the Welsh Assembly election, 2007.
The new boundaries define two constituencies covering the preserved county of Powys, both entirely within its boundary.

For Welsh Assembly elections, constituencies are grouped into additional member

Additional Member System

The Additional Member System is the term used in the United Kingdom for the mixed member proportional representation voting system used in Scotland, Wales and the London Assembly....

 electoral regions, and changes to constituency boundaries mean, also, changes to regional boundaries.

Boundaries for the three existing constituencies were defined before changes to the boundaries of preserved counties under the Preserved Counties (Amendment to Boundaries) (Wales) Order 2003, which came into effect in 2003, and before changes to local government boundaries under the Local Government (Wales) Act 1994

Local Government (Wales) Act 1994

The Local Government Act 1994 is an Act of the Parliament of the United Kingdom which created the current local government structure in Wales of 22 unitary authority areas, referred to as principal areas in the Act, and abolished the previous two-tier structure of counties and districts...

, which came into effect in 1996.

Current boundaries

Constituency	Boundaries
1. Brecon and Radnorshire CC (Westminster) Brecon and Radnorshire (UK Parliament constituency) Brecon and Radnorshire is a county constituency of the House of Commons of the Parliament of the United Kingdom. Created in 1918, it elects one Member of Parliament by the first past the post system of election; until 1997 its name was simply Brecon and Radnor.The Brecon and Radnorshire Welsh...
2. Montgomeryshire CC (Westminster) Montgomeryshire (UK Parliament constituency) Montgomeryshire is a constituency represented in the House of Commons of the Parliament of the United Kingdom. Created in 1542, it elects one Member of Parliament , traditionally known as the knight of the shire, by the first-past-the-post system of election.The Montgomeryshire Welsh Assembly...

2005 election boundaries

Constituency	Boundaries
1. Brecon and Radnorshire CC (Westminster) Brecon and Radnorshire (UK Parliament constituency) Brecon and Radnorshire is a county constituency of the House of Commons of the Parliament of the United Kingdom. Created in 1918, it elects one Member of Parliament by the first past the post system of election; until 1997 its name was simply Brecon and Radnor.The Brecon and Radnorshire Welsh...
2. Montgomeryshire CC (Westminster) Montgomeryshire (UK Parliament constituency) Montgomeryshire is a constituency represented in the House of Commons of the Parliament of the United Kingdom. Created in 1542, it elects one Member of Parliament , traditionally known as the knight of the shire, by the first-past-the-post system of election.The Montgomeryshire Welsh Assembly...
3. Clwyd South CC (Westminster) Clwyd South (UK Parliament constituency) Clwyd South is a constituency of the House of Commons of the Parliament of the United Kingdom . The constituency was created in 1997, and it elects one Member of Parliament by the first past the post method of election.The Clwyd South Welsh Assembly constituency was created with the same...  (part)

The Clwyd South constituency was also partly a Clwyd constituency.

1999 to 2007

Constituency	Assembly region	Constituency boundaries
1. Brecon and Radnorshire CC (Assembly)	Mid and West Wales
2. Montgomeryshire CC (Assembly)
3. Clwyd South CC (Assembly) Clwyd South (National Assembly for Wales constituency) Clwyd South is a constituency of the National Assembly for Wales. It elects one Assembly Member by the first past the post method of election...  (part)	North Wales

The Clwyd South constituency is also partly a Clwyd constituency.

The Mid and West Wales region includes also five Dyfed constituencies and one which is partly a Gwynedd constituency and partly a Clwyd constituency.
The North Wales region includes also five constituencies which are wholly Clwyd constituencies, two which are partly Clwyd constituencies and partly Gwynedd constituencies, and one which is wholly a Gwynedd constituency.

From 2007

Constituency	Assembly region	Constituency boundaries
1. Brecon and Radnorshire CC (Assembly)	Mid and West Wales
2. Montgomeryshire CC (Assembly)

The Mid and West Wales region will include, also, five Dyfed constituencies and one Gwynedd constituency.