The population of the Republic has doubled since 1961 and is now at its higest level since records began in 1861.
There are now 4,234,925 people living in the State, according to preliminary figures released by the Central Statistics Office (CSO) today.
The figures - which were compiled during the April Census - show the population has risen by 318,000 since 2002, a rise of 8.1 per cent over the four years, or by 2 per cent per annum.
The figures show the population has risen by a dramatic 50 per cent since 1961, when it was recorded at 2.8 million.
The number of non-Irish nationals living in the Republic has almost doubled since the last Census in 2002, when it was approximately 220,000. It is now estimated at 400,000 which represents between 9 and 10 per cent of the total population.
Looked at from a 10 year perspective Ireland's population is growing by 1.6 per cent per annum. This is the highest rate of growth in the EU, ahead of Cyprus and Luxembourg.
The three countries were the only in the European Union to experience growth rates of over 1 per cent in the ten-year period.
Fastest growing counties in the State since 2002 were Fingal (+22.1 per cent), Meath (+21.4) and Kildare (+13.5). A third of the total population increase over the last 10 years has been in these three counties.
The population of Leinster as a whole outstripped the national average increase of 8.1 per cent during the four-year period - rising by 8.9 per cent or from 2,105,579 to 2,292,939.
The population of Connacht also eclipsed the national rate of increase - rising by 8.4 per cent or from 464,296 to 503,083.
Ulster's population (that of Cavan, Donegal and Monaghan) equalled the national rate of increase of 8.1 per cent - rising from 246,714 to 266,733.
But significantly Munster's population only rose by 6.5 per cent or from 1,100,614 to 1,172,170.
Cork City and Limerick City were the only two of the 34 administrative regions to register a fall in population during the 2002-2006 period.
A CSO spokesman said the decline in these two areas could not be attributed to the large number of people who had traveled to Dublin to attend the Heineken Cup semi-final between Munster and Leinster during the period.
Apart from Fingal, there was a relatively modest increase of just 20,000 in the rest of Dublin meaning the overall population of Dublin grew by just 5.6 per cent - considerably less than the 8.1 per cent increase for the State as a whole.
