LLANLLUAN-with-TRECASTELL (LLAN-LLWYN), a hamlet, in the parish of LLANARTHNEY, hundred of ISCENNEN, county of CARMARTHEN, SOUTH WALES, 91 miles (E. s.E.) from Carmarthen: the population is included in the return for the pariah. It lies near the northern declivity of the Mynydd Mawr, and takes its name from an ancient chapel which formerly existed here.