Rh_o(D) immune globulin (RhIG) is a medication used to prevent RhD isoimmunization in mothers who are RhD negative and to treat idiopathic thrombocytopenic purpura (ITP) in people who are Rh positive. It is often given both during and following pregnancy. It may also be used when RhD-negative people are given RhD-positive blood. It is given by injection into muscle or a vein. A single dose lasts 12 weeks. It is made from human blood plasma.

Common side effects include fever, headache, pain at the site of injection, and red blood cell breakdown. Other side effects include allergic reactions, kidney problems, and a very small risk of viral infections. In those with ITP, the amount of red blood cell breakdown may be significant. Use is safe with breastfeeding. Rho(D) immune globulin is made up of antibodies to the antigen Rh_o(D) present on some red blood cells. It is believed to work by blocking a person's immune system from recognizing this antigen.

Rh_o(D) immune globulin came into medical use in the 1960s, following the pioneering work of John G. Gorman. In 1980, Gorman shared the Lasker-DeBakey Clinical Medical Research Award for pioneering work on the rhesus blood group system.

RhIG is on the World Health Organization's List of Essential Medicines.