Shalane Blackwood, from Sinfin, was found unresponsive at HMP Nottingham on the morning of Wednesday, August 5. The cause of death is unknown and a file is being prepared for the coroner.
Blackwood was jailed for conspiracy to possess a shotgun in August 2012 and was on licence recall.
A Prison Service spokesman said: “CPR was attempted but he was pronounced dead at 6.52am by paramedics. As with all deaths in custody, the independent prisons and probation ombudsman will conduct an investigation.”