Johann Ludwig Wilhelm Thudichum (August 27, 1829 – September 7, 1901) was a German physician and biochemist who was a native of Büdingen.
He studied medicine in Giessen, where he also worked in the laboratory of chemist Justus von Liebig (1803-1873). In 1853 he moved to London, where he worked for the remainder of his career.
Thudichum was a pioneer in the field of neurochemistry, and a founder of "brain chemistry". He performed chemical analyses of over one thousand human and animal brains, and specialized in pathological chemistry. He is credited with the identification and characterization of numerous compounds of the brain, including cephalin, sphingomyelin, galactose, lactic acid and sphingosine. In 1884 he described his research in a publication titled "A Treatise on the Chemical Constitution of the Brain", which was widely criticized and rejected at the time by many in the scientific community. After his death, the discoveries from Thudichum's research have been realized as important scientific contributions to the study of the chemical and molecular composition of the brain.
Thudichum published over eighty works, including books on non-medical topics such as viticulture and cookery. He also devised a specialized nasal speculum that is still in use by physicians today. Since 1974 the "Thudichum Medal Lecture" is awarded in England for outstanding achievements in the field of neurochemistry, and at Yale University, the "Thudichum Post–Doctoral Research Fellowship in Neuro-oncology" is granted for the research of brain tumors.