The rarest blood type in the world is Rh-null, often referred to as the “golden blood”. It lacks all 61 possible antigens in the Rh system, making it extremely rare — only about 1 in 6 million people have it. Due to its universal compatibility within the Rh system, it’s in high demand for transfusions, but it must be used very sparingly because so few donors exist.
In terms of the more common ABO and Rh blood groups, AB-negative (AB-) is the rarest, found in only about 1% of the global population.