Llangiwg or Llanguicke is an ancient parish in the very north-west of Glamorgan, adjacent to the borders with Brecknockshire and Carmarthenshire. It forms part of the hundred of Llangyfelach. The northern and north-western boundaries are formed by the county border with Carmarthenshire; the north-eastern boundary is formed by the county border with Brecknockshire; the south-western boundary is formed by the Upper Clydach River; and the south-eastern boundary is formed by the River Tawe.
The parish encompasses Gwaun-Cae-Gurwen, Pontardawe, Ystalyfera and Lower Brynamman. The parish church is dedicated to St Ciwg and is a Grade-I-listed building. Part of the tower is Norman, dating back to the 13th century, with the aisle dating back to the 16th century. It is situated on Llanguicke Road to the south of the parish. It was closed and it was put up for sale in 2004. It was purchased by the Friends of Llangiwg in 2007, a voluntary organisation comprising members of the local community.