William ap Thomas

Sir William ap Thomas
The tomb of William ap Thomas
Died	1445 London
Resting place	Abergavenny Priory, Abergavenny
Occupation(s)	Politician, Knight, Courtier
Title	Sir
Spouse(s)	Elizabeth Bluet Gwladys ferch Dafydd Gam
Children	4 (including William Herbert, 1st Earl of Pembroke)
Parent(s)	Sir Thomas ap Gwyllym (died 1438) Maud Morley

Sir William ap Thomas (died 1445) was a Welsh nobleman, politician, knight, and courtier. He was a member of the Welsh gentry family that came to be known as the Herbert family through his son William Herbert, 1st Earl of Pembroke (8th creation) and is the agnatic ancestor, via an illegitimate descendant of the 1st Earl of the 8th creation, of the current Herbert family of the Earl of Pembroke and Montgomery, and also of the Herbert Earl of Carnarvon.

William ap Thomas purchased the manor and lordship of Raglan (including the castle at Raglan) in 1430 for 1000 marks from his step-son, James Berkeley (1394-1463), Knt., 6th Lord Berkeley, son of William's wife, Elizabeth Bluet, and her second husband, Sir James Berkeley (1353-1405). No children came of the William ap Thomas and Elizabeth Bluet marriage. The castle was greatly expanded by William and his son, William Herbert, into the well-fortified Raglan Castle, one of the finest late medieval Welsh castles.

William served King Henry V of England during his first French campaign and in numerous subsequent capacities and was knighted in 1426.