The incident took place at approximately 8.30am in the Patrician Park area on Kill Avenue. Gardaí confirmed that the scene has been secured while forensic examinations are carried out.
The victim's body remains at the location pending a post-mortem examination, and the Coroner has been informed.
Investigators have established an incident room at Dún Laoghaire Garda Station, with a senior investigating officer leading the inquiry.
Several roads, including Kill Avenue and Glenageary Road Upper, have been closed to facilitate the investigation. Traffic diversions are currently in place, while Dublin Bus has advised passengers to expect delays on its E2 service between Dún Laoghaire and Harristown.
Gardaí are carrying out house-to-house enquiries in the area and are appealing to anyone who may have witnessed the incident to come forward.
Motorists who travelled along Kill Avenue between 8am and 9am and who may have dash-cam or other video footage are also urged to contact investigators.
Anyone with information is asked to contact Dún Laoghaire Garda Station on 01 666 5000, the Garda Confidential Line on 1800 666 111, or any Garda station.
