Baron Penrhyn is a title that has been created twice. 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. This creation became extinct on his death in 1808. 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. Lord Penrhyn was the younger brother of George Douglas, 17th Earl of Morton. 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.
Lord Penrhyn was succeeded by his eldest son George Sholto, the second Baron. He also represented Carnarvon in Parliament as a Conservative. On his death the title passed to his son Edward Sholto, the third Baron. He was a Conservative Member of Parliament for Northampton South. He was succeeded by his son Hugh Napier, the fourth Baron. He notably served as Lord Lieutenant of Caernarvonshire from 1933 to 1941. On his death in 1949 the line of the eldest son of the first Baron failed. He was succeeded by his first cousin once removed, the fifth Baron. He was the son of the Hon. Archibald Charles Henry Douglas-Pennant, second son of the first Baron. Lord Penrhyn was 101 years and 74 days when he died on 3 February 1967 and was then the oldest ever hereditary peer. This record was not surpassed until the death of the seventh Viscount St Vincent in September 2006. He was succeeded by his son, the sixth Baron. As of 2014[update] the title is held by the latter's nephew, the seventh Baron, who succeeded in 2003. As a descendant of the fourteenth Earl of Morton he is also in remainder to this peerage and its subsidiary title the lordship of Dalkeith.