Marcel Claude Bessis (15 November 1917 – 28 March 1994) was a French physician known for research on blood cells.

[5] Later he studied exchange transfusion as a treatment for hemolytic disease of the newborn, uremia and acute leukemia.

[1][3] He invented new instruments to aid his research and developed techniques for manipulating cells using laser microbeams.

[1] Bessis wrote that "The doctor who knows how to see can recognize in a red cell the subtle alteration of a gene transmitted from time immemorial on the banks of the Congo River or the marks of aggressions of daily life.

In 1948 he was appointed director of research at the Centre national de transfusion sanguine [fr] (National Centre of Blood Transfusion), serving in that role until 1966,[5] when he became the founding director of the Institut de Pathologie cellulaire (Institute of Cell Pathology) at INSERM.