This entry defines criminal sanctions by distinguishing them from civil sanctions, briefly surveys major categories of criminal sanctions, and outlines the primary social justifications for using such sanctions—focusing on deterrence as a distinct purpose of punishment. To develop these ideas more rigorously, the entry describes a basic economic model of criminal offending. This model highlights the conditions under which the threat of criminal sanctions can influence individual behavior in predictable and potentially socially useful ways. The entry also examines how various forms of criminal sanctions relate to deterrence, and it concludes with a brief assessment of key empirical findings that shed light on the effectiveness of sanctions in practice.