The first creation came in the Peerage of Ireland in 1783 in favour of Richard Pennant, who had previously served as a Member of Parliament for Petersfield and Liverpool.
The next creation came in 1866 in the Peerage of the United Kingdom when the Conservative politician Edward Douglas-Pennant was created Baron Penrhyn, of Llandegai in the County of Carnarvon.
He had previously represented Carnarvon in the House of Commons and also served as Lord Lieutenant of Caernarvonshire.
He was granted the estate of his father-in-law (a cousin and heir of the first Baron of the 1783 creation) on the condition that he accepted his wife's maiden name, Pennant.
In 1833 he had married Juliana Isabella Mary Pennant (died 1842), eldest daughter and co-heiress of George Hay Dawkins-Pennant of Penrhyn Castle and in 1841 he assumed by Royal licence the additional surname of Pennant.