Castlebar has recorded a slight slip to 12th place in the latest IBAL survey.
Ballymun in Dublin is the worst litter blackspot in the country.
The latest Irish Business Against Litter survey shows Kilkenny sparkles as the cleanest city nationwide.
Litter levels rose in 24 of the 37 towns and cities inspected at the end of 2020, with only 17 being deemed to be clean.
Across the region Sligo and Castlebar were ranked as clean to European norms at 11th and 12th place respectively.
The An Taisce report for Castlebar noted that it was a good result, but a slight slip in cleanliness of the town, with a number of heavily littered sites to blame.
The two offending sites were the N5 Business Park and the Main Street.
Some sites within Castlebar just missed getting the top litter grade, like St. Brid’s Primary School and the N5 Dublin and N84 Galway / Ballinrobe approaches to the town.
In the moderately littered category came Galway City Centre and Roscommon in 19th and 20th place, while Galway Inner City- Ballybane ranked 26th.
IBAL spokesperson, Conor Horgan says Kilkenny had stiff competition to claim the top spot: