KIDWELLY (Cydweli)  , a decayed market-town and municipal borough of Carmarthenshire, Wales, situated (as its name implies) near the junction of two streams, the Gwendraeth Fawr and the Gwendraeth Fach, a short distance from the shores of Carmarthen Bay . Pop . (1901), 2285 . It has a station on the Great Western railway . The chief attraction of Kidwelly is its magnificent and well-preserved castle, one of the finest in South Wales, dating chiefly from the 13th century and admirably situated on a knoll above the Gwendraeth Fach . The parish church of St Mary, of the 14th century, possesses a lofty tower with a spire . The quiet little town has had a stirring history . It was a place of some importance when William de Londres, a companion of Fitz Hamon and his conquering knights, first erected a castle here . In 1135 Kidwelly was furiously attacked by Gwenllian, wife of Griffith ap Rhys, prince of South Wales, and a battle, fought close to the town at a place still known as Maes Gwenllian, ended in the total defeat and subsequent execution of the Welsh princess . Later, the extensive lordship of Kidwelly became the property through marriage of Henry, earl of Lancaster, and to this circumstance is due the exclusive jurisdiction of the town . Kidwelly received its first charter of incorporation from Henry VI.; its present charter dating from 1618 . The decline of Kidwelly is due to the accumulation of sand at the mouth of the river, and to the consequent prosperity of the neighbouring Llanelly .