The International Society of Blood Transfusion (ISBT) is a scientific society founded in 1935. The society aims to promote the study of blood transfusion, and to spread the know-how about the manner in which blood transfusion medicine and science best can serve the patient's interests. The society's central office is in Amsterdam, and there are over 1700 members in around 100 countries. Currently, the President of the ISBT Board of Directors is Martin L. Olsson.
The Society organizes an international congress every even-numbered year and two regional congresses in odd years, one in Europe and one in another continent. ISBT advocates standardisation and harmonisation in the field of blood transfusion. The other major impact on the transfusion community is the classification of various Human blood group systems under a common nomenclature. ISBT's coordination also extends to obtaining donors with rare antigens, a process that often involves international searches, and a common terminology is critical to that process.