- Aberavon 1918-
- Aberdare 1950-1983
- Aberdeen 1708-1885
- Aberdeen Central 1997-2005
- Aberdeen North 1885-
- Aberdeen South 1885-
- Aberdeen and Glasgow Universities 1868-1918
- Aberdeenshire 1708-1868
- Aberdeenshire East 1950-1983
- Aberdeenshire Eastern 1868-1918
- Aberdeenshire West 1950-1983
- Aberdeenshire West and Kincardine 1997-
- Aberdeenshire Western 1868-1918
- Aberdeenshire and Kincardineshire Central 1918-1950
- Aberdeenshire and Kincardineshire Eastern 1918-1950
- Abertillery 1918-1983
- Abingdon 1660-1983
- Accrington 1885-1983
- Acton 1918-1974
- Airdrie and Shotts 1997-
- Aldborough 1660-1832
- Aldeburgh 1660-1832
- Aldershot 1918-
- Aldridge-Brownhills 1974-
- Altrincham 1885-1945
- Altrincham and Sale 1945-1997
- Altrincham and Sale West 1997-
- Alyn and Deeside 1983-
- Amber Valley 1983-
- Amersham 1660-1832
- Andover 1660-1918
- Anglesey 1660-1983
- Angus 1997-
- Angus East 1983-1997
- Angus North and Mearns 1974-1983
- Angus South 1974-1983
- Anstruther Easter Burghs 1708-1832
- Antrim 1802-1885
- Antrim 1922-1950
- Antrim East 1922-
- Antrim East 1885-1922
- Antrim Mid 1885-1922
- Antrim North 1922-
- Antrim North 1885-1922
- Antrim South 1922-
- Antrim South 1885-1922
- Appleby 1660-1832
- Appleby 1885-1918
- Arfon 1885-1918
- Argyll 1708-1983
- Argyll and Bute 1983-
- Armagh 1922-1983
- Armagh 1802-1885
- Armagh 1832-1885
- Armagh Mid 1885-1922
- Armagh North 1885-1922
- Armagh South 1885-1922
- Arundel 1660-1868
- Arundel 1974-1997
- Arundel and Shoreham 1950-1974
- Arundel and South Downs 1997-
- Ashburton 1660-1918
- Ashfield 1955-
- Ashford 1885-
- Ashton-under-Lyne 1832-
- Aston Manor 1885-1918
- Athlone 1832-1885
- Aylesbury 1660-
- Ayr 1950-2005
- Ayr District of Burghs 1708-1950
- Ayr, Carrick and Cumnock 2005-
- Ayrshire 1708-1868
- Ayrshire Central 1974-1983
- Ayrshire Central 2005-
- Ayrshire North and Arran 2005-
- Ayrshire North and Bute 1974-1983
- Ayrshire Northern 1868-1918
- Ayrshire South 1974-1983
- Ayrshire Southern 1868-1918
2,145 constituencies in total