A 38-year-old inmate has died at Parc Prison in Bridgend.
Next of kin have been informed after his death on Friday, and the prison said its thoughts were with his “family and friends at this difficult time”.
It will be investigated by the Prisons and Probation Ombudsman as with all prison deaths, according to HMP Parc.
It is a category B men’s prison for adult and young adult offenders which held more than 1,600 prisoners at the time of an inspection in 2019.
It is operated by G4S Care and Justice Ltd as the only privately-run prison in Wales, and opened in 1997.
A prison spokesperson said: “Staff at HMP Parc take the health and wellbeing of prisoners extremely seriously.
“We provide an extensive range of services including a dedicated safeguarding officer on site and all prisoners have 24 hours access to the Samaritans lines as well as being able to speak to Samaritan trained prisoners about their mental health.
“We also provide an in-house health care team. All of our staff undertake mental health training during their employment.”