Robert Powell Vaughan (?1592 – 16 May 1667) was an eminent Welsh antiquary and collector of manuscripts. His collection, later known as the Hengwrt-Peniarth Library from the houses in which it was successively preserved, formed the nucleus of the National Library of Wales, and is still in its care.
Vaughan was born at Gwengraig, Dolgellau, around 1592. Very little is known of his early life, but he was recorded as entering Oriel College, Oxford in 1612, though he left without taking his degree. He later settled at the mansion of Hengwrt (English: Old Court), Llanelltyd, also near Dolgellau, which had belonged to his mother's family. Vaughan was active in the legal affairs of Merioneth and served on its Commission of the peace.
Vaughan's main interests lay in the early history of Wales and in genealogy. Though these were common enough pursuits for the rural gentry of the time, Vaughan devoted himself to them with great energy and diligence, as well as to the collection of early manuscripts and books which he amassed at Hengwrt, preserving many unique texts which might otherwise have been lost. He was able to increase his holdings further after making an arrangement with the calligrapher and manuscript collector John Jones of Gellilyfdy, Flintshire, in which one would combine both collections on the other's death. Vaughan also transcribed texts himself, carried out genealogical research, made an English translation of the Brut y Tywysogion (or Chronicle of the Princes), and wrote several short historical tracts as well as the book British Antiquities Revived, first published at Oxford in 1662.