Transcarceration describes the movement of individuals between different forms of state control and confinement, rather than their release from it. In legal practice across England and Wales, Scotland, Northern Ireland and Ireland, it commonly refers to people shifted between prison, immigration detention, secure hospitals, secure children’s homes, approved premises, community justice settings and other closed or highly supervised environments.The term is not usually defined in legislation or case law; it is a descriptive, criminological and socio‑legal concept increasingly used in sentencing, penal policy, mental health law, youth justice and immigration detention commentary. It is relevant when assessing whether apparent “decarceration” (for example, diversion from prison to secure mental health facilities) in fact maintains or expands overall systems of detention and supervision.For legal practitioners, transcarceration is significant when advising on proportionality, human rights impacts (particularly under the ECHR and the Irish Constitution), conditions and lawfulness of detention, and equality implications for groups disproportionately subject to multiple forms of confinement. Usage and meaning are broadly consistent across the UK and Ireland, although the specific statutory frameworks (e.g. mental health, immigration, youth justice and public protection regimes) vary by jurisdiction.