The Chicago Police Department (CPD) is the primary law enforcement agency of the city of Chicago, Illinois, United States, under the jurisdiction of the Chicago City Council. It is the second-largest municipal police department in the United States, behind the New York City Police Department. As of 2022 CPD had 11,710 sworn officers on duty, and in 2020 had over 948 other employees. Tracing its roots to 1835, the Chicago Police Department is one of the oldest modern police departments in the world.

A law enforcement agency (LEA) is any government agency responsible for law enforcement within a specific jurisdiction through the employment and deployment of law enforcement officers and their resources. The most common type of law enforcement agency is the police, but various other forms exist as well, including agencies that focus on specific legal violation, or are organized and overseen by certain authorities. They typically have various powers and legal rights to allow them to perform their duties, such as the power of arrest and the use of force.