Iestyn is a masculine given name. Notable people with the name include:
Iestyn (saint), Welsh saint of the 6th or 7th centuries Justinian of Ramsey Island, 6th-century hermit Iestyn Davies, British opera singer Iestyn ap Gwrgant (1045–1093), the last ruler of the Welsh kingdom of Morgannwg Iestyn Edwards, stage and TV writer/performer, published poet and journalist Iestyn Harris (born 1976), Welsh professional rugby league footballer Iestyn Thomas (born 1976), Welsh rugby union footballer Rhydderch ap Iestyn (died 1033), king of Gwent and Morgannwg in south Wales