Marcel Claude Bessis (15 November 1917 – 28 March 1994) was a French physician known for research on blood cells. Bessis was born in Tunis on 15 November 1917. He was educated at the Lycée Janson-de-Sailly in Paris, France. He developed an interest in microscopy in his teenage years and went on to study medicine at the University of Paris. During the Second World War, he served as a military physician and pioneered the technique of exchange transfusion to treat war injuries. He graduated with a medical degree in 1944. Later he studied exchange transfusion as a treatment for hemolytic disease of the newborn, uremia and acute leukemia. He was a frequent collaborator of Jean Bernard.