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.

The castle at Raglan, attained through his marriage to an heiress, Elizabeth Bluet, 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.