Ireland (Irish: Éire [ˈeːɾʲə] ^ⓘ), also known as the Republic of Ireland (Poblacht na hÉireann), is a country in Northwestern Europe. It consists of 26 of the 32 counties of the island of Ireland, with a population of about 5.4 million. Its capital and largest city is Dublin, on the eastern side of the island, with a population of over 1.5 million. The sovereign state shares its only land border with Northern Ireland, which is part of the United Kingdom. It is otherwise surrounded by the Atlantic Ocean, with the Celtic Sea to the south, St George's Channel to the south-east and the Irish Sea to the east. It is a unitary, parliamentary republic. The legislature, the Oireachtas, consists of a lower house, Dáil Éireann; an upper house, Seanad Éireann; and an elected president (Uachtarán) who serves as the largely ceremonial head of state, but with some important powers and duties. The head of government is the Taoiseach (prime minister, lit. 'chief'), elected by the Dáil and appointed by the president, who appoints other government ministers.

The Irish Free State was created with Dominion status in 1922, following the Anglo-Irish Treaty. In 1937, a new constitution was adopted, in which the state was named "Ireland" and effectively became a republic, with an elected non-executive president. It was officially declared a republic in 1949, following The Republic of Ireland Act 1948. Ireland became a member of the United Nations in 1955. It joined the European Communities (EC), the predecessor of the European Union (EU), in 1973. The state had no formal relations with Northern Ireland for most of the 20th century, but the 1980s and 1990s saw the British and Irish governments working with Northern Irish parties to resolve the conflict that had become known as the Troubles. Since the signing of the Good Friday Agreement in 1998, the Irish government and Northern Irish government have co-operated on a number of policy areas under the North/South Ministerial Council created by the Agreement.

Ireland is a developed country with a quality of life ranked sixth in the world by the 2024 Human Development Index Report adjusted for inequality. It also ranks highly in healthcare, economic freedom and freedom of the press. According to the Global Peace Index, Ireland was the second most peaceful country worldwide in 2024.

It is a member of the EU and a founding member of the Council of Europe and the OECD. The Irish government has followed a policy of military neutrality through non-alignment since before World War II, and the country is consequently not a member of NATO, although it is a member of the Partnership for Peace and certain aspects of PESCO. Ireland's economy is advanced, with one of Europe's major financial hubs being centred on Dublin. It ranks among the top five wealthiest countries in the world in terms of both GDP and GNI per capita. After joining the EC, the country's government enacted a series of liberal economic policies that helped to boost economic growth between 1995 and 2007, a time now often referred to as the Celtic Tiger period. A recession and reversal in growth then followed during the Great Recession, which was exacerbated by the bursting of the Irish property bubble. The Great Recession lasted until 2014, and was followed by a new period of strong economic growth.

The names Ireland and Éire both derive from Old Irish Ériu, which in turn comes from Proto-Celtic ɸīweriyū meaning "fertile soil". The Classical Latin name for the island of Ireland, Ivernia, also comes from this same root, and it remains a popular, poetic synonym for Ireland to this day (usually respelled "Hibernia", under the influence of hibernum, the Latin word for "winter").

The state created in 1922, comprising 26 of the 32 counties of Ireland, was "styled and known as the Irish Free State" (Saorstát Éireann). The Constitution of Ireland, adopted in 1937, says that "the name of the State is Éire, or, in the English language, Ireland". Section 2 of the Republic of Ireland Act 1948 states, "It is hereby declared that the description of the State shall be the Republic of Ireland." The 1948 Act does not name the state "Republic of Ireland", because to have done so would have put it in conflict with the Constitution.

The government of the United Kingdom used the name "Eire" (without the diacritic) and, from 1949, "Republic of Ireland", for the state. It was not until the 1998 Good Friday Agreement, when the state dropped its claim to Northern Ireland, that it began calling the state "Ireland".

The state is also informally called "the Republic", "Southern Ireland" or "the South"; especially when distinguishing the state from the island or when discussing Northern Ireland ("the North"). Irish republicans reserve the name "Ireland" for the whole island and often refer to the state as "the Free State", "the 26 Counties", or "the South of Ireland". This is a "response to the partitionist view [...] that Ireland stops at the border".