Penology is a subfield of criminology that deals with the philosophy and practice of various societies in their attempts to repress criminal activities and satisfy public opinion via an appropriate treatment regime for persons convicted of criminal offenses. The term penology comes from "penal," Latin poena, "punishment," and the Greek suffix -logia, "study of". Penology is concerned with the effectiveness of social processes devised and adopted for the prevention of crime, via the repression or inhibition of criminal intent via the fear of punishment. The study of penology deals with the treatment of prisoners and the subsequent rehabilitation of convicted criminals.

Penology concerns many topics and theories, including those concerning prisons (prison reform, prisoner abuse, prisoners rights, and recidivism), as well as theories of the purposes of punishment (deterrence, retribution, incapacitation, and rehabilitation). Contemporary penology concerns itself mainly with criminal rehabilitation and prison management.

Penology is a multidisciplinary field that draws from sociology, psychology, law, and other disciplines. It is broadly classified into different categories, including comparative penology, which is the study of the differences and similarities in criminal justice systems and correctional practices in different countries and cultures.

The importance of penology lies in its critical role in the criminal justice system. It helps to ensure that offenders are punished in a manner that is consistent with the law and ethical principles. It also plays a role in deterring crime and protecting society by imposing sanctions on offenders. By studying different types of prisons and alternative forms of punishment, penologists can determine what works best for different types of offenders.