Keep Prisons Single Sex (KPSS) was a campaign launched in 2020 to defend the sex-based rights of women held in prison in England, Wales and Scotland. It argued that women in custody — many of whom have histories of male violence and abuse — have the right to be accommodated away from male prisoners, regardless of how those prisoners identify. The campaign also pressed for sex registered at birth to be recorded and used in criminal-justice data collection, risk assessment and service provision. Although the UK campaign closed in 2024, its sister campaign in the United States continues this work.