Individuals with type 1 diabetes or advanced type 2 diabetes suffer insufficient insulin secretion, leading to symptoms of hyperglycemia. To maintain the normal blood glucose levels, those people with diabetes must administer insulin multiple times a day. However, insulin requirements are influenced by several factors such as diet, exercise, and illness, combined with the narrow therapeutic index, making accurate insulin dosage challenging. Excessive insulin administration can even pose life-threatening risks. In addition, frequent daily insulin injections place considerable physiological and psychological burdens on patients. To tackle these challenges, researchers have embarked on the development of closed-loop insulin delivery systems. These systems adjust insulin dosages in real-time changes based on the patient’s blood glucose levels, therefore enhancing both the safety and effectiveness of insulin therapy. This review categorizes closed-loop insulin delivery systems into two types: electronic-based and material-based systems, based on their compositional attributes. The exploration of both types covers their components, developmental history, clinical applications, current pros and cons, and future directions. The relative strengths and limitations of these two categories of closed-loop insulin delivery systems are also compared and discussed.