Within the conventional ABO and Rh blood group system, the rarest blood groups in India are AB-, B-, and AB+. Several rare phenotypes have also been identified in India, some of which fall outside the standard ABO/Rh classification. These include the Bombay (hh) phenotype, Rh-null, P-null (Pk), -D-/-D-, In(a+b-), Colton-null (Co(a–b–)), weak ABH variants, I–i-, and EMM-negative.