St Ellyw's Church, Llanelli, is situated within a triangular churchyard, whose south and east boundaries are delineated by Bridge Street (south) and Thomas Street (east). The green and adjacent A484, to the immediate north-west of the churchyard, is depicted on historic (1880-1915) Ordnance Survey mapping as a built-up area, including housing, public house and town hall. This area comprised Wind Street, Union Square, Cil-heol and Upper Church Street.

The church is first mentioned in documents of the eleventh century and was a parish church in the medieval period. In the thirteenth century the living was in the patronage of Patrick de Chatworth, Lord of Kidwelly. After his death the patronage passed to the Crown. In the late fourteenth century, the tithes were appropriated by John of Gaunt to the collegiate church of St Mary, Leicester. Until the reformation the parish had four subordinate chapels.

The church is a Grade II* listed building constructed of rock-faced rubble stone with red sandstone dressings. It consists of three-bayed chancel, four-bayed nave, two-bayed north chapel (above below-ground boiler house), two-bayed south chapel/ vestry, north and south transepts, south porch and three-storeyed west tower. The octagonal font is thought to be medieval. The tower dates from the early sixteenth century. Four bells are known to have been present in the sixteenth century. The church was restored in 1683. Wall paintings in the church include the Hanoverian Royal Arms.

In 1839 it consisted of nave, chancel, north (depicted as 'Glyn Chapel') and south (depicted as 'Berwick Chapel') transepts, west tower and south porch. An account from 1849 described the church as much modernised and cruciform in plan, its tower being only feature to preserve its original character. Drawings preceding the 1905 restoration show a lean-to vestry north of the chancel west bay and a transeptal school room and lean-to coalhouse north of the tower. The church (except tower) was rebuilt in 1905-1907 to the designs of E.M Bruce Vaughan, Cardiff or G.F Bodwin, London (sources differ).

Sources include:
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, pp. 48
Richard Suggett, Painted Temples: Wallpaintings and Rood-screens in Welsh Churches, 1200–1800, (RCAHMW 2021)

RCAHMW 2022