CSO population and migration estimates show that the population rose by 97,600 people in the 12 months to the end of April 2023, which was the largest 12-month increase since 2008.
There were 141,600 immigrants – a 16-year high.
This was the second successive 12-month period where over 100,000 people immigrated to Ireland.
Of those immigrants, 29,600 were returning Irish citizens, 26,100 were other EU citizens, and 4,800 were British citizens.
The CSO said that close to 30,000 of those people who came back to Ireland in the 12 months to April 2023 were returning Irish citizens.
The remaining 81,100 immigrants were citizens of other countries –including almost 42,000 Ukrainians.
Over 64,000 people departed the State in the 12 months to April 2023, compared with 56,100 in the same period of 2022.
This was one of the highest figures of recent years.
Of those who left the country, just over 30,000 were Irish citizens, so net migration was close to zero in terms of the Irish.
Natural increase of 20,000
There was a natural increase of 20,000 people in the State, comprising 55,500 births and 35,500 deaths.
Statistician Cathal Doherty said: "Ireland's population was estimated to be 5.28 million, rising by 97,600 people in the year to April 2023. This was the largest 12-month population increase since 2008, when the population rose by 109,200.
“The number of immigrants, or those entering the State, in the year to April 2023 was estimated to be 141,600, while the number of emigrants, or those leaving the State, over the same period was estimated at 64,000.
“These combined flows gave positive net migration (more people having arrived than left), of 77,600 in the year to April 2023, compared with 51,700 in the previous year.”
There were 806,300 people living in Ireland aged 65 and over in April 2023.
This cohort showed an increase in population share between 2017 and 2023 (increasing from 13.6% to 15.3% of the total), a volume increase of 153,900 people.
There were 1,338,700 people living in Ireland aged 45-64 in April 2023. This age grouping also had a rise in population share between 2017 and 2023, growing from 24.1% to 25.3% of the total, a volume increase of 180,800 people.
Looking at where people reside, the proportion of the population living in Dublin has increased from 27.6% of the total in 2011 to 28.4% of the total in 2023 and now stands at 1,501,500 people, the CSO said.