Sir Richard de Grenville (died after 1142) (alias de Grainvilla, de Greinvill, etc.) was one of the Twelve Knights of Glamorgan who served under Robert FitzHamon (died 1107), in the conquest of Glamorgan in Wales. He obtained from FitzHamon the lordship of Neath in which he built Neath Castle and in 1129 founded Neath Abbey. He is by tradition the founder and ancestor of the prominent Westcountry Grenville family of Stowe in the parish of Kilkhampton in Cornwall and of Bideford in Devon, the later head of which family was John Granville, 1st Earl of Bath (1628–1701). The surname of his supposed descendants the Westcountry Grenville family was spelled by tradition "Grenville" until 1661 when it was altered to "Granville".