Carlow edged out Trim, Co Meath, for the top spot in the survey of 53 towns and cities around Ireland, conducted by Irish Business Against Litter (IBAL).
Longford was in third place, followed by Wexford and Drogheda.
IBAL had also published the details of those further down the list at the weekend, highlighting the poor state of Cork and Dublin in particular.
The capital was ranked a lowly 50th while Cork came second bottom of the league.
While 39 towns were classed as ‘litter-free’, IBAL expressed concern over the littered state of Cork and Dublin.
Six litter black spots were also identified in both cities, at a time when many other towns around the country have been improving their responses to litter.
IBAL chairman Dr Tom Cavanagh said recommendations made to government on how to tackle littering in larger cities had “fallen on deaf ears”, at a time when the country needed to project a better image internationally.
“We had hoped for some meaningful measures from Minister Gormley in 2010, but none were delivered.”
IBAL had sought a new tax on conventional chewing gum, with a view to developing a market for degradable gum. It also demanded cleaning schedules for national routes which already happens on roads in the North.
IBAL also wants a defined amount within the €45m allocated to local authorities by the National Roads Authority specifically for cleaning up litter.
“In addition, a report on dumping was promised, but has failed to materialise as yet. None of these issues has been acted upon, so it is no wonder that the entry points to Dublin and Cork in particular are still blighted by litter,” Dr Cavanagh said.
No such problems for Carlow, which has won the title of cleanest town in Ireland in the IBAL league for the third time in its nine years.
An Taisce, who conducted the litter surveys, said: “All sites surveyed in Carlow were Grade A. There were litter awareness and/or dog fouling notices at all of the sites surveyed — perhaps the constant reminder of same is having the desired effect.
“Well done to all who work so diligently to present Carlow at its best and to the citizens who co-operate so enthusiastically.”
To celebrate, Carlow will receive a number of trees for planting, provided by the Irish Tree Centre based in Co Cork.