Carmarthen Town South was an electoral ward, representing part of the community of Carmarthen, Carmarthenshire, Wales. Much of its southern border was defined by the River Towy, with the Carmarthen Town North and Carmarthen Town West wards to the north.

In 2014, the Carmarthen Town South electoral ward had an electorate of 2,896.^[1] The total population was 3,785, of whom 70.6% were born in Wales. The 2011 census indicated that 38.2% of the population were able to speak Welsh.^[1]

Carmarthen Town South was an electoral ward since the 1940s. It was previously known as Carmarthen Town No.2 Ward. It became a two-member electoral ward for the purposes of elections to Carmarthenshire County Council. It corresponded to the South ward which elects five members to Carmarthen Town Council.

From 1973 until 1996 it was a single-member ward for the purposes of elections to Dyfed County Council and a two-member ward for elections to Carmarthen District Council.

Following a boundary review by the Local Democracy and Boundary Commission for Wales, Carmarthen Town South was merged with Carmarthen Town North to be called Carmarthen Town North and South, effective from the May 2022 local elections. The new ward saw an overall reduction in councillors from four to three.^[2]

Since 2017 the ward was represented by Plaid Cymru councillors Gareth John and Alun Lenny.