To the nearest million what is the approximate population of The Republic of Ireland?

Ireland also known as the Republic of Ireland is a sovereign state in north-western Europe occupying 26 of 32 counties of the island of Ireland. The capital and largest city is Dublin, which is located on the eastern part of the island, and whose metropolitan area is home to around a third of the country's 4.75 million inhabitants. The state shares its only land border with Northern Ireland, a part of the United Kingdom. It is otherwise surrounded by the Atlantic Ocean, with the Celtic Sea to the south, Saint George's Channel to the south-east, and the Irish Sea to the east.

The 1922 state, comprising 26 of the 32 counties of Ireland, was "styled and known as the Irish Free State". The Constitution of Ireland, adopted in 1937, provides 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 as "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 that it used the name "Ireland".