Hermann Ludwig Eichhorst (3 March 1849 – 26 July 1921) was a German-Swiss internist
Eichhorst was born in Königsberg. He studied medicine in Königsberg and Berlin, and was an assistant to Ernst Viktor von Leyden (1832–1910), Bernhard Naunyn (1839–1935), and Friedrich Theodor von Frerichs (1819–1885). In 1884 became director of the medical clinic in Zürich, where he remained for the rest of his career.
Eichhorst made contributions in several fields of medicine. In an 1878 monograph he documented one of the earliest descriptions of progressive pernicious anemia. He also discovered globular forms in the poikilocytosis of this disease, which were to become known as "Eichhorst's corpuscles". In 1896 and 1913 respectively, Eichhorst provided early accounts of infantile and hereditary multiple sclerosis. He also described a form of interstitial neuritis that is sometimes referred to as "Eichhorst's neuritis".