Neath Castle (Welsh: Castell Nedd) is a Norman castle located in the town centre of Neath, Wales. Its construction was begun by Robert, Earl of Gloucester, the nominal Lord of Glamorgan, at a date estimated between 1114 and 1130.^[1][2] It is also referred to as "Granville's Castle", after Richard I de Grenville (or Granville or Glanville; died post 1142), Lord of Neath, who has also been credited with its construction.^[3] The town of Neath takes its Welsh name, "Castell-nedd", from the castle.^[4]

The first castle in Neath was located west of the river^[1] near the Roman fort of Nidum, and was a timber fortification in a motte and bailey structure.^[5] When Richard de Grenville founded Neath Abbey close by, he abandoned this original castle, and it may have been used by the monks as a source of building material.^[6]

A second castle on the opposite bank of the river, in what is now the centre of the town, is first documented in 1183; shortly afterwards, William de Cogan, son of Miles de Cogan, was appointed constable.^[7] This second castle was built by Gilbert de Clare, 5th Earl of Gloucester.^[8] During the 13th century, being a Norman stronghold, it was subject to attack by the Welsh, notably by Llywelyn the Great, who captured it in 1231 with help from a local Welsh lord, Morgan Gam.^[1][5][9] Following this, it was substantially rebuilt by Richard de Clare, 6th Earl of Gloucester, Gilbert's son.^[10]

It was taken again, and this time destroyed, by Humphrey de Bohun, 4th Earl of Hereford, in 1321, during the rebellion against King Edward II of England.^[11] Its owner, Hugh Despenser the Younger (who had gained the lordship through his marriage to the heiress Eleanor de Clare), rebuilt it, possibly with the addition of a gatehouse.^[10] In 1376, one Roger Kyngot was the constable,^[12] and the castle was rebuilt in stone in 1377; that is probably when the great gatehouse was built, which is the main surviving feature.^[13] The castle was in use until the 17th century, and has been a recreational area for the town since the 18th century.^[14] The post of "Constable of Neath Castle", a medieval legacy, was held by Sir Humphrey Mackworth from 1703.^[15] The title was eventually absorbed into that of Mayor of Neath. What remains of the castle is designated a Grade II* listed building.^[16]

• List of castles in Wales
• Castles in Great Britain and Ireland
• List of Scheduled Monuments in Neath Port Talbot