Douglas Ross Hyde (Irish: Dubhghlas de hÍde; 17 January 1860 – 12 July 1949), known as An Craoibhín Aoibhinn (lit. transl. the pleasant little branch), was an Irish academic, linguist, scholar of the Irish language, politician, and diplomat who served as the first president of Ireland from June 1938 to June 1945. He was a leading figure in the Gaelic revival, and the first president of the Gaelic League, one of the most influential cultural organisations in Ireland at the time.

Hyde was born at Longford House in Castlerea, County Roscommon, while his mother, Elizabeth Hyde (née Oldfield; 1834–1886), was on a short visit. His father, Arthur Hyde, whose family was originally from Castlehyde near Fermoy, County Cork, was Church of Ireland rector of Kilmactranny, County Sligo, from 1852 to 1867, and it was here that Hyde spent his early years. Arthur Hyde and Elizabeth Oldfield married in County Roscommon, in 1852, and had three other children: Arthur Hyde (1853–79 in County Leitrim), John Oldfield Hyde (1854–96 in County Dublin), and Hugh Hyde (1856).

In 1867, his father was appointed prebendary and rector of Tibohine, and the family moved to neighbouring Frenchpark, in County Roscommon. He was home-schooled by his father and his aunt due to a childhood illness. While a young man, he became fascinated with hearing the old people in the locality speak the Irish language. He was influenced in particular by the gamekeeper Séamus Hart and his friend's wife, Mrs. Connolly. Aged 14, Hyde was devastated when Hart died, and his interest in the Irish language—the first language he began to study in any detail, as his own undertaking—flagged for a while. However, he visited Dublin several times and realised that there were groups of people, just like him, interested in Irish, a language looked down on at the time by many and seen as backward and old-fashioned.

Rejecting family pressure that, like past generations of Hydes, he would follow a career as an Anglican clergyman, Hyde instead became an academic. He entered Trinity College Dublin, where he became fluent in French, Latin, German, Greek, and Hebrew, graduating in 1884 as a moderator in modern literature. A medallist of the College Historical Society, he was elected its president in 1931. His passion for the language revival of Irish, which was already in severe decline, led him to help found the Gaelic League, or in Irish, Conradh na Gaeilge, in 1893.

Hyde married German-born but British-raised Lucy Kurtz in 1893. The couple had two daughters, Nuala and Úna.

Hyde joined the Society for the Preservation of the Irish Language around 1880, and between 1879 and 1884, he published more than a hundred pieces of Irish verse under the pen name An Craoibhín Aoibhinn (lit. transl. the pleasant little branch).

Initially derided, the Irish language movement gained a mass following. Hyde helped establish the Gaelic Journal in 1892; in November, he wrote a manifesto called The necessity for de-anglicising the Irish nation, arguing that Ireland should follow its own traditions in language, literature, and dress.

In 1893, he helped found Conradh na Gaeilge (the Gaelic League) to encourage the preservation of Irish culture, music, dance and language. A new generation of Irish republicans (including Pádraig Pearse, Éamon de Valera, Michael Collins and Ernest Blythe), became politicised through their involvement in Conradh na Gaeilge. Hyde filled out the 1911 census form in Irish.