Gibson, William (Mac Giolla Bhríde, Liam) (1868–1942), 2nd Baron Ashbourne , Irish-language activist, was born 16 December 1868 in Dublin, eldest child of Edward Gibson (qv), 1st Baron Ashbourne, and Frances Maria Adelaide Gibson (née Colles). He had two brothers and a sister, Violet, who attempted to assassinate Mussolini in April 1926. He was educated at Harrow before studying arts in TCD and proceeding to an MA in philosophy at Merton College, Oxford. While in Oxford he converted to catholicism, founding the Roger Bacon Society there. He wrote a number of books on religious subjects, including The abbé Lamennais and the liberal catholic movement in France (1896), L'église libre dans l'état libre (1907) and Grégoire and the French revolution: a study (1932). These titles are also evidence of his Francophilia. In January 1896 he married Marianne de Monbrison, the daughter of a protestant French aristocrat. She too converted to catholicism and they divided their time between France, London, and Ireland.
At TCD he became interested in the Irish language. He joined the London branch of the Gaelic League, attended classes in London and Dublin, and was soon fluent. His mode of dress (a saffron coat and kilt and long cloak, which he buckled at the shoulder with a large brooch) was an ostentatious display of his commitment to cultural nationalism. He is attired in this manner in a portrait contained in the Poole collection in the National Photographic Archive, Dublin. He worked hard to promote the language. Among the groups he addressed were the Literary and Historical Society in UCD (1903) and the students of St Enda's (1910). In 1911 he gave financial support to St Enda's. He was a regular contributor to Guth na nGaedheal, the journal of the Gaelic League in London, and was president of the London branch (1908–14). He was a delegate to numerous ard-fheiseanna and became a member of the coiste gnó (executive). As early as 1910 he spoke out against the politicisation of the organisation. Indeed, his resignation as president of the London branch was a product of this trend. He disagreed with the league's attitude towards the first world war because his love of France proved stronger than his antipathy to Britain.
In 1913 his father died and he succeeded to the barony, but did not take his seat in the house of lords until 1918. He addressed the house once (27 June 1918), delivering a portion of his speech in Irish. In 1914 he had urged Irish MPs to address parliament in Irish. In 1926 he relieved the Gaelic League of a debt of £1,000 and was unanimously elected president (1928). He was re-elected every year until 1932, but then resigned because he disagreed with the league's opposition to independent feiseanna. His love of languages extended to French and German (in which he was fluent) and Polish and Welsh (in which he was competent).
He had no children. When he died at Compiegne, Oise, France, on 21 January 1942 he was succeeded by his nephew, Edward Russell Gibson.