Gamma globulins are a class of proteins in the blood, identified by their position after serum protein electrophoresis. The most significant gamma globulins are antibodies.

Gamma globulin injections are sometimes given in an attempt to temporarily boost a patient's immunity against disease. Injections are most commonly used on patients who have been exposed to hepatitis A or measles. Such injections are less common in modern medical practice than they were previously, and injections of gamma globulin previously recommended for travellers have largely been replaced by the use of hepatitis A vaccine.