Llanelli is a constituency of the House of Commons of the Parliament of the United Kingdom. From 1918 to 1966 the official spelling of the constituency name was Llanelly. It elects one Member of Parliament (MP) by the first past the post system of election.

The Borough of Llanelli was one of thirty-seven local government districts in Wales from 1974 to 1996. It was the smallest of six districts in the newly-created county of Dyfed, and was formed under the Local Government Act 1972 by a merger of the municipal boroughs of Llanelli and Kidwelly, Burry Port urban district and Llanelli Rural District all in the former administrative county of Carmarthenshire. The district was governed by Llanelli Borough Council which was based in the town of Llanelli.

Llanelli is a constituency of the National Assembly for Wales. It elects one Assembly Member by the first past the post method of election. Also, however, it is one of eight constituencies in the Mid and West Wales electoral region, which elects four additional members, in addition to eight constituency members, to produce a degree of proportional representation for the region as a whole.