Amicus curiae describes a person or body that is not a party to proceedings but assists the court by offering impartial submissions on points of law or wider public interest. The term (Latin for “friend of the court”) is used across the UK and Ireland, largely consistently, as a descriptive expression rather than a tightly defined statutory concept. In practice, an amicus curiae is typically invited or permitted by the court to file written submissions, and sometimes to make oral submissions, where their expertise or perspective may help the court reach a properly informed decision. They do not represent any party and owe their primary duty to the court. In England and Wales, the role overlaps with, but is not identical to, the Advocate to the Court or Advocate General interventions (for example, by the Attorney General or the Equality and Human Rights Commission). Similar mechanisms exist in Scotland, Northern Ireland and Ireland, sometimes under labels such as interveners or third‑party interveners. Amicus curiae participation is most common in appellate courts and constitutional or human rights litigation, especially where the decision may have significant legal or systemic implications beyond the immediate parties.