The cardiopulmonary bypass (CPB) machine, originally used in 1953 by John Heysham Gibbon Jr., is a complex specialized device that includes an extracorporeal circuit. This circuit temporarily reroutes blood outside the body, fully supporting cardiopulmonary function and, when necessary, undergoing treatment or modification. While maintaining the body’s cardiopulmonary and vascular functions, it also provides the surgeon with a bloodless, motionless field, facilitating not only cardiac procedures but also major vascular and thoracic surgeries. Though the CPB machine has evolved significantly over the last 70 years, its fundamental concepts have remained unchanged. The CPB machine draws blood from the patient (most often from the venous vasculature or right side of the heart), drains the blood into a closed or open reservoir, filters it, oxygenates it, warms/cools it, and then returns it to the patient arterial vasculature beyond the heart and lungs. This shunting of blood away from the patient to the CPB machine and back allows for hemodynamic stability while the heart or lungs are operated on. Understanding the structure and function of the CPB machine and its role as an extracorporeal circuit is essential for the entire team involved in cardiac surgery. It fosters a collaborative and informed approach to patient care. To fully grasp the overall concepts of CPB and its complexities, one must understand the components of the CPB machine. This chapter provides an overview of the fundamentals of CPB machine equipment.