United Nations Convention Against Torture

Convention against Torture is a treaty of international human rights law created by United Nations on December 10 1984 that prohibits all kind of torture, any cruel, inhuman and degrading punishment or treatment harming the person's dignity. The Convention entered into force on 26 June 1987. As of April 2022, 173 countries has ratified the Convention.
The Convention is supervised by the Committee Against Torture. 
The Convention also has the optional protocol that enables national or international organization for human rights investigators to research the prisons in a country that ratifies the protocol for knowing if any torture or inhuman treatments or punishments prohibited by the Convention are done. As of April 2022, 91 countries has ratified the protocol.