Éamon de Valera ( AY-mən DEH-və-LAIR-ə, -⁠LEER-; Irish: [ˈeːmˠən̪ˠ dʲɛ ˈwalʲəɾʲə]; first registered as George de Valero; changed some time before 1901 to Edward de Valera; 14 October 1882 – 29 August 1975) was an American-born Irish statesman and political leader. He served as the president of Ireland from 1959 to 1973, and three terms as prime minister (titled as President of the Executive Council of the Irish Free State from 1932 to 1937 and as Taoiseach from 1937 to 1948, 1951 to 1954, and 1957 to 1959). He had a leading role in introducing the Constitution of Ireland in 1937, and was a dominant figure in Irish political circles from the early 1930s to the late 1960s, when he served terms as both the head of government and head of state.

De Valera was a commandant of the Irish Volunteers (Third Battalion) at Boland's Mill during the 1916 Easter Rising. He was arrested and sentenced to death, but released for a variety of reasons, including his American citizenship and the public response to the British execution of Rising leaders. He returned to Ireland after being jailed in England and became one of the leading political figures of the War of Independence. After the signing of the Anglo-Irish Treaty, de Valera served as the political leader of Anti-Treaty Sinn Féin until 1926, when he, along with many supporters, left the party to set up Fianna Fáil, a new political party which abandoned the policy of abstentionism from Dáil Éireann in favour of republicanising the Irish Free State from within.

From there, de Valera went on to be at the forefront of Irish politics until the turn of the 1960s. He took over as president of the Executive Council from W. T. Cosgrave and later became Taoiseach, with the adoption of the Constitution of Ireland in 1937. With a total of 21 years in office, he is the longest serving Irish head of government by total days served in the post. He resigned in 1959 upon his election as president of Ireland. By then, he had been the founding Leader of Fianna Fáil for 33 years and he, along with older founding members, began to take a less prominent role relative to newer ministers such as Jack Lynch, Charles Haughey and Neil Blaney. De Valera served as President of Ireland from 1959 to 1973, two full terms in office.

De Valera's political beliefs evolved from militant Irish republicanism to strong social, cultural and fiscal conservatism. He has been characterised as having a stern and unbending, and also devious demeanour. His roles in the Civil War have also been interpreted as making him a divisive figure in Irish history. Biographer Tim Pat Coogan sees his time in power as being characterised by economic and cultural stagnation, while Diarmaid Ferriter argues that the stereotype of de Valera as an austere, cold, and even backward figure was largely manufactured in the 1960s and is misguided.