Trinity College has fallen from 88th place to 104th over the last year
Most Irish universities have fallen in the latest world rankings.
The annual QS World University Ranking grades institutions on a range of factors.
Staff to student ratios, academic reputation and employer reputation are all taken into account.
Trinity College in Dublin - the only country to have previously made the top 100 - has fallen to 104th place.
It's down from 88th position last year, and has also dropped more than 40 places compared to a rank of 61 in 2014.
UCD has fallen 25 places to 193, while NUI Galway has dropped from 243 to 260 over the last year.
UCC and DCU are also down - to positions 338 and 422 respectively.
However, both Maynooth and the University of Limerick have avoided a drop - but neither of them make it into the top 500.
Academics are blaming the poor performance on a lack of investment in higher education.
President of NUI Galway, Professor Ciarán Ó hÓgartaigh, said: “We are on a flat curve where small changes make for a potentially large change in our rankings.
"In that context, we will continue to focus on what makes a difference for our students and for our society, drawing on the strengths of our hinterland to further enhance our international reputation and reach."
He added: “Investment in education is critically important as Ireland’s consistent source of economic and social development."