The deceased, Brendan Gahan from Tallaght, was serving a sentence for drug-related offences when he was reportedly stabbed at the prison on Thursday night.
Prison officers are understood to have responded after a disturbance was reported in a cell, where they found Gahan unresponsive.
An internal investigation has been launched by the Irish Prison Service, while An Garda Síochána is also investigating the circumstances surrounding the death.
The Irish Prison Service confirmed that a prisoner died in custody at Wheatfield Prison on 13 August 2026.
In a statement, the service said all deaths in custody are subject to investigation by the Irish Prison Service and the Inspector of Prisons, with Gardaí also becoming involved where appropriate.
The cause of death will ultimately be established by the Coroner's Office.
The Irish Prison Service said it wished to extend its condolences to Gahan's family and friends, adding that his next of kin had been notified.
The investigation remains ongoing.
