This chapter provides an overview of mental illness and mental health services for those in institutional correctional settings such as jails and prisons. Framed within a global context, the chapter first summarizes the current research related to mental health and illness for incarcerated populations. Emphasis is placed on the global prevalence of mental disorders and important social correlates of mental illness for those in jails and prisons. Following this, the chapter examines current policies regarding mental health service provision for incarcerated populations in different national contexts. Special attention is paid to countries like the United States where mental health service provision in institutional correctional settings is particularly controversial. The chapter concludes with a discussion of the policy and practice implications of the current literature as well as opportunities for future research on mental health and services in institutional correctional settings.