Sir Richard I de Grenville (d.post 1142) ("alias" de Grainvilla, de Greinvill, etc.) was one of the Twelve Knights of Glamorgan who served in the Norman Conquest of Glamorgan under his elder brother Robert FitzHamon (died 1107), the first Norman feudal baron of Gloucester and Lord of Glamorgan from 1075. He obtained from FitzHamon the lordship of Neath, Glamorgan, in which he built Neath Castle and in 1129 founded Neath Abbey. Richard de Grenville was one of three (or four) known sons of Hamo Dapifer (died "circa" 1100) Sheriff of Kent, an Anglo-Norman royal official under both King William the Conqueror (1066–1087) and his son King William Rufus (1087–1100). 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.