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 Seamus 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 a number of 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 in the Church, 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 Irish, already a language in severe decline, led him to help found the Gaelic League, or in Irish, Conradh na Gaeilge, in 1893.

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.

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

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.

Uncomfortable at the growing politicisation of the movement, Hyde resigned the presidency in 1915. He was succeeded by the League’s co-founder Eoin MacNeill.

Hyde had no association with Sinn Féin and the independence movement. He was elected to Seanad Éireann, the upper house of the Irish Free State’s Oireachtas (parliament), at a by-election on 4 February 1925, replacing Sir Hutcheson Poë.

In the 1925 Seanad election, Hyde placed 28th of the 78 candidates, with 19 seats available. The Catholic Truth Society opposed him for his Protestantism and publicised his supposed support for divorce. Historians have suggested that the CTS campaign was ineffective, and that Irish-language advocates performed poorly, with all those endorsed by the Gaelic League losing.

In April 1938, by now retired from academia, Hyde was plucked from retirement by Taoiseach Éamon de Valera and again appointed to Seanad Éireann. Again his tenure proved short, even shorter than before; however, this time it was because Hyde was chosen, after inter-party negotiations—following an initial suggestion by Fine Gael—to be the first President of Ireland, to which office he was elected unopposed. He was selected for a number of reasons:

Hyde was inaugurated as the first President of Ireland, on 26 June 1938. The Irish Times reported it as follows:

Despite being placed in a position to shape the office of the presidency via precedent, Hyde by and large opted for a quiet, conservative interpretation of the office. His age and health obligated him to schedule periods of rest throughout his days, and his lack of political experience caused him to defer to his advisers on questions of policy and discretionary powers, especially to his Secretary, Michael McDunphy. On 13 November 1938, just months after Hyde’s inauguration, Hyde attended an international soccer match between Ireland and Poland at Dalymount Park in Dublin. This was seen as breaching the GAA’s ban on ‘foreign games’ and he was subsequently removed as patron of the GAA, an honour he had held since 1902.

However, after a massive stroke in April 1940, plans were made for his lying-in-state and state funeral. However, Hyde survived, albeit paralysed and having to use a wheelchair.

Although the role of President of Ireland was largely ceremonial, Hyde did make important decisions during his presidency. He was confronted with a crisis in 1944, when de Valera’s government unexpectedly collapsed in a vote on the Transport Bill and the President had to decide whether or not to grant a dissolution of the Dáil to de Valera. Under the Constitution the President of Ireland may grant or refuse a dissolution of the Dáil to a Taoiseach who has “ceased to retain the support of a majority in Dáil Éireann”. If a dissolution is granted, a general election is proclaimed to fill the seats now vacated by the dissolution. However, this means that for four to six weeks, until the new Dáil assembles, there is no Dáil. Fearing this gap might facilitate an invasion during World War II, during which no parliament could be called upon to deal with the invasion, the Oireachtas enacted emergency legislation (under Article 28.3.3°) – the General Elections (Emergency Powers) Act 1943 – which allowed an election to be called separate from a dissolution, with the Dáil only being dissolved just before new Dáil would assemble, so ensuring the gap between Dála (plural of Dáil) would be too short to facilitate an invasion. Under the Act the President could “refuse to proclaim a general election on the advice of a Taoiseach who had ceased to retain the support of a majority in Dáil Éireann”.

One of Hyde’s last presidential acts was a visit to the German Ambassador Eduard Hempel, on 3 May 1945, to offer his formal condolences on the death of Adolf Hitler. The visit remained a secret until 2005.

Hyde left office on 25 June 1945, opting not to nominate himself for a second term. Owing to his ill-health he did not return to his Roscommon home, Ratra, empty since the death of his wife early in his term. He moved into the former residence of the Secretary to the Lord Lieutenant, in the grounds of Áras an Uachtaráin, which he renamed Little Ratra, where he lived out the remaining four years of his life. He died at 10pm on 12 July 1949, aged 89.