A survey of over 40 Irish towns, cities and urban districts has found that litter levels continued to fall in 2013.
The study, carried out by Irish Business Against Litter, showed 83% of towns and cities are now deemed to be as clean as, or cleaner than, their European counterparts.
Of 42 towns and cities, 19 were cleaner than the European average, with a further 16 in line with the average.
Kilkenny was named the cleanest city in Ireland for the second year running, with Cavan in second place and Tramore in third.
It is the first time a town or city has retained the title.
Dublin city centre ended the year as clean for the first time, but the capital's north inner city remains a litter blackspot.
"With Dublin City attaining litter-free status, we can say without reservation that Ireland has never been so clean," said IBAL Chairman Dr Tom Cavanagh.
"I want to acknowledge the efforts of the local authorities in bringing this about."
The environs of Dublin Airport slipped down to 37th out of 42 areas surveyed in the league.
"We have focused heavily on the roads from the airport, as these present the first impression of our country for 90% of visitors by air to Ireland and should be a showpiece for the entire country," said Dr Cavanagh.
"But while the airport grounds themselves are spotless, the roads from it are littered.
"Tourism Ireland invests hugely in selling Ireland as a green, unspoilt island and the country needs to live up to this image from the moment visitors set foot here. Clearly, this isn't the case."