Franz Ernst Christian Neumann (30 January 1834 – 6 March 1918) was a German pathologist who was a native of Königsberg. His common name was Ernst Neumann.

He was the son of physicist Franz Ernst Neumann (1798–1895), and grandson of chemist Karl Gottfried Hagen (1749–1829). He had two noted brothers, mathematician Carl Gottfried Neumann (1832–1925) and economist Friedrich Julius Neumann [de] (1835–1910).

In 1855 he obtained his doctorate from Albertina Universität Königsberg, where one of his instructors was Hermann von Helmholtz. He performed post-graduate studies in Prague, and in Berlin under Rudolf Virchow (1821–1902). From 1866 until 1903 he was in charge of the Pathological Institute at Konigsberg. Neumann was awarded honorary degrees from the Universities of Tübingen (1898) and Geneva (1914). In 1995, the first International Ernst Neumann Award has been initiated by the 24.Meeting of "International Society for Experimental Hematology in Düsseldorf/ Germany. The first recipient of this award was Donald Medcalf from Melbourne ()

Ernst Neumann made many contributions in the field of hematology. He demonstrated that erythropoiesis and leukopoiesis formulate in the bone marrow. "Ernst Neumann postulated a common stem cell for all hematopoietic cells".

In 2007, Zech et al. wrote: "The beginning of Stem Cell research can be dated back to Ernst Neumann, who was appointed professor of pathology at Koenigsberg in 1866 and described in a preliminary communication the presence of nucleated red blood cells in bone marrow (BM) saps. He concluded in his subsequent papers, that during postembryonic life, erythropoiesis and leukopoiesis are taking place in the BM. On the basis of his observation, Ernst Neumann was the first to postulate the BM as blood forming organ with a common SC for all hematopoietic cells"

"Among his "firsts" were the identification of leukemia and of pernicious anemia as diseases of the marrow. He coined the term myelogeneous leukemia, (today's acute myeloid leukemia), and described in 1882 the law of dissemination concerning yellow and red bone marrow: "Again, it was Neumann who provided us with the classic statement. In 1882, he enunciated the rule governing the development of yellow marrow. In effect, he recognized a phenomenon that is sometimes referred to us as "Neumann's law". It states that at birth all bones that contain marrow contain red marrow. With age, the blood producing activity contracts toward the center of the body, leaving the more peripheral bones with only fatty marrow. For about 50 years, students of the marrow did not know what to make of this phenomenon"

Neumann was supported by Giulio Bizzozero and by Claude Bernard, Alexander Maximov and Artur Pappenheim, but there were also Rudolf Virchow, Paul Ehrlich, Pouchet and Georges Hayem to repudiate him. "Despite all the opposition, however, within two decades, Neumann's discovery was a scientific axiom! The brilliance of the truth may first be blinding, but ultimately it supersedes all artificial illuminators"

In 1871, Neumann described congenital epulis (CE) of the newborn. Neumann also published an early work on medical electrodiagnosis and formed the name "Hämosiderin" as hematological pigment.