HM Prison Belmarsh
| Location | Western Way, Thamesmead, London, SE28 0EB | 
|---|---|
| Security class | Adult Male/Category A | 
| Capacity | 792 | 
| Population | 675 (as of August 2021) | 
| Opened | 1991 | 
| Managed by | HM Prison Services | 
| Governor | Jenny Louis | 
| Website | Belmarsh at justice.gov.uk | 
His Majesty's Prison Belmarsh is a Category A men's prison located in Thamesmead, south-east London, England. Belmarsh Prison is run by His Majesty's Prison Service and is situated next to HMP Isis and HMP Thameside. The prison is used for high-profile cases, particularly those concerning national security. Within the grounds of the prison is the High Security Unit (HSU), consisting of 48 single cells.
Belmarsh is also nicknamed "Hellmarsh," owing to the high number of physical and authority abuses reported by both the prison's inmates (including former politician Jeffrey Archer, who coined the name and was imprisoned there for four years for perjury), and by human rights activists.