StephenJudge
From the Ordinance Survey Ireland Open Data sets, released under Creative Commons CC-BY 4.0; the english name spelling is "Dunleary". See https://data-osi.opendata.arcgis.com/datasets/centres-of-population-osi-national-placenames-gazetteer?geometry=-6.159%2C53.281%2C-6.128%2C53.299

However other spellings are commonly used and excepted by state bodies. These alternatives are:
Dun Learey
Dun Laoghaire
Dún Laoghaire 