Carmarthen East and Dinefwr (Welsh: Dwyrain Caerfyrddin a Dinefwr) was a constituency of the House of Commons of the Parliament of the United Kingdom last represented since 2010 by Jonathan Edwards of Plaid Cymru.

[3] The constituency was within the Carmarthenshire authority area, with Llanybydder, Llandovery and Llanfihangel-ar-Arth in the north, Llanfihangel-uwch-Gwili, Llanegwad, and Llandeilo in the central area, and Ammanford and Glanamman in the south.

Boundary changes for the 2010 general election introduced minor alterations, with the areas around Hermon and Llanpumsaint removed to the Carmarthen West and South Pembrokeshire constituency.

The constituency includes the whole of 41 Carmarthenshire communities (Abergwili; Ammanford; Betws; Cenarth; Cilycwm; Cwmamman; Cynwyl Gaeo; Dyffryn Cennen; Gorslas; Llanarthney; Llanddarog; Llanddeusant; Llandeilo; Llandovery; Llandybie; Llandyfaelog; Llanegwad; Llanfair-ar-y-bryn; Llanfihangel Aberbythych; Llanfihangel-ar-Arth; Llanfihangel Rhos-y-Corn; Llanfynydd; Llangadog; Llangathen; Llangeler; Llangunnor; Llangyndeyrn; Llanllawddog; Llanllwni; Llansadwrn; Llansawel; Llanwrda; Llanybydder; Llanycrwys; Manordeilo and Salem; Myddfai; Newcastle Emlyn; Pencarreg; Quarter Bach; St Ishmael; Talley).

Of the 65 rejected ballots: Of the 145 rejected ballots: Edwards was elected as a Plaid Cymru MP, but had the whip withdrawn by the party after he was arrested on suspicion of assault in May 2020.