Llangyndeyrn (Welsh pronunciation^ⓘ) is a village, community and electoral ward in the River Gwendraeth valley, Carmarthenshire, in Dyfed region of West Wales, United Kingdom. The village name is often spelt as Llangendeirne.

Llangyndeyrn Welsh: Llangyndeyrn
Llangyndeyrn Location within Carmarthenshire
Population	3,102 [1]
OS grid reference	SN457140
Community	Llangyndeyrn
Principal area	Carmarthenshire
Preserved county	Dyfed
Country	Wales
Sovereign state	United Kingdom
Post town	LLANELLI
Postcode district	SA15
Post town	KIDWELLY
Postcode district	SA17
Dialling code	01269
Police	Dyfed-Powys
Fire	Mid and West Wales
Ambulance	Welsh
UK Parliament	Carmarthen East and Dinefwr
Senedd Cymru – Welsh Parliament	Carmarthen East and Dinefwr
List of places UK Wales Carmarthenshire 51°48′12″N 4°14′21″W / 51.8033°N 4.2393°W / 51.8033; -4.2393

The Welsh language name of the village means "the church of St. Cyndeyrn". A Welsh saint named Cyndeyrn is the equivalent of the English Kentigern and the Scottish St. Mungo; but the St Cyndeyrn associated with Llangyndeyrn is believed to be a different one, a descendant of Cunedda whose festival is on 5/6 August.

Both St Cyndeyrn's parish church and Capel Salem are grade II* listed buildings.^[2] Nearby is the remains of Banc y Betws, or Betws Castle, a motte-and-bailey castle.

The small village is well known for its resistance against the attempt to flood the village in order to create a reservoir for the Borough of Swansea.

Within the village is the Ysgol Y Fro school for infants.

The community is bordered by the communities of: Llangunnor; Llanddarog; Pontyberem; Llanelli Rural; Trimsaran; Kidwelly; and Llandyfaelog, all being in Carmarthenshire and includes the villages of Pontyates, Carway and Meinciau.