Imanuentius is named in some manuscripts of Julius Caesar's De Bello Gallico as a king of the Trinovantes, the leading nation of south-eastern Britain at that time, who ruled before Caesar's second expedition to the island in 54 BC. Variant spellings include Inianuvetitius, Inianuvetutus and Imannuetitius. In other manuscripts this king's name is not given. John Koch suggests that the original form of Imanuentius's name may have been *Mannuētios. He also suggests that the Welsh mythological figure Manawydan may derive from an earlier *Mannuētiagnos, "son of Mannuetios".