The majority of Irish speakers (55%) say they cannot speak the language well, according to Census 2022.
One in ten people who speak Irish can do so very well, while a further 32% speak it well.
Almost 1.9 million people - aged three and over - said that they could speak Irish, an increase of more than 112,500, or 6%, since Census 2016.
The highest proportions of these were recorded in Co Galway (50%) and Co Clare (47%),
The lowest were in Dublin city (33%) and Co Louth (35%).
The towns with the highest proportions of daily at Irish speakers - at 69% - are An Bun Beag in Co Donegal and An Cheathrú Rua in Co Galway.
The figures also show that, in April 2022, 106,000 people were living in Gaeltacht areas - a rise of over 6,600 (7%) compared with April 2016.
The proportion of Irish speakers in Gaeltacht areas continued to decrease from 69% in 2011 to 66% in 2022.
Among non-Irish citizens, the group with the highest proportion of Irish speakers was Australians with 15%, or 501 people, aged three and over able to speak the language.
CSO Statistician Deirdre Lynch said the number of people who speak Irish on a daily basis decreased slightly, by 2%, since Census 2016 while the figure for those who said they never spoke the language increased by 13%.
Speaking on RTÉ's News at One, Ms Lynch said that what she "found particularly interesting is when we look at frequency of Irish spoken by single year of age we can actually see that the school-goers are those who are speaking it probably most frequently within the education system.
"Between the ages of four and 19 people are exclaiming that they speak it more often ... and that they're speaking it well or very well whereas this does drop off quite a bit from the ages of 19 to 25, and then 25 to 30, and 35 on.
"However, when we look at those aged 65 years and over, we can actually see that just under one third [of them] can speak Irish and a large proportion of those say they can speak it well".
Almost 50% people aged 15+ have third-level qualification
The Census 2022 statistics show that 45% of people aged 15 and over had a third-level qualification, up from 35% in 2011.
Almost 270,000 people, or 8%, had completed their full-time education before they were aged 16, down from 10% in 2016.
People aged 15 and over in the Dún Laoghaire-Rathdown area of Dublin were the most likely to have a third-level education (65%).
The average age nationally at which people finished their full-time education, according to Census 2022, was 20.8 years.
