Eglwys Dewi Sant or St David's Church, was an Anglican parish church in the town of Carmarthen, Carmarthenshire, Wales. Built in the 1830s and briefly considered as a possible replacement cathedral for the dioceses of St David's, the church eventually became the home of Carmarthen's main Welsh-speaking Anglican congregation. The church closed in the early twenty-first century after the building became unsafe.

Carmarthen is the county town of Carmarthenshire and a community in Wales, lying on the River Towy 8 miles (13 km) north of its estuary in Carmarthen Bay. The population was 14,185 in 2011, down from 15,854 in 2001, but gauged at 16,285 in 2019. It has a claim to be the oldest town in Wales – Old Carmarthen and New Carmarthen became one borough in 1546. It was the most populous borough in Wales in the 16th–18th centuries, described by William Camden as "chief citie of the country". Growth stagnated by the mid-19th century as new settlements developed in the South Wales Coalfield.