Emil von Behring (German: [ˈeːmiːl fɔn ˈbeːʁɪŋ] ^ⓘ; Emil Adolf von Behring: born Emil Adolf Behring; 15 March 1854 – 31 March 1917), was a German physiologist who received the 1901 Nobel Prize in Physiology or Medicine, the first one awarded in that field, for his discovery of a diphtheria antitoxin. He was widely known as a "saviour of children", as diphtheria used to be a major cause of child death. His work with the disease, as well as tetanus, has come to bring him most of his fame and acknowledgment. He was honoured with Prussian nobility in 1901, henceforth being known by the surname "von Behring".

Behring was born in Hansdorf, Kreis Rosenberg, Province of Prussia (now Ławice, Iława County, Poland). His father was a schoolmaster; the family had 13 children.

Between 1874 and 1878, Behring studied medicine at the Kaiser-Wilhelm-Akademie in Berlin, an academy for military doctors, since his family could not afford the university. As a military doctor, he studied the action of iodoform. Due to his work on Neurotomia opticociliaris (or optociliary neurotomy), Behring became a doctor from the institute and later was able to pass his exam for licensed work in his area of Marburg. In 1878, his service required him to be sent to Poland where he focused on septic diseases. His potential was becoming well known to many. This led to his commanded return to Prussia to study with Robert Koch. He was employed by the military as he received his grants and money from the Prussian army. For each semester of education, he owed one year of service as a military surgeon. This accumulated to two years, from 1881 to 1883 as he served under the Second Hussar regiment. A lesser known part of his studies was his research in ophthalmology and how he furthered the understanding of the eye and its diseases. He wrote a paper during his time at Wicherkiewicz's hospital in Poznań from 1881 to 1883 on an eye tumor case that ended up with the patient dying from leukemia, but it did allow for much needed research on treatments for the eye and what the preferred pathways for surgery would be. He learned under some of the great ophthalmologists such as Carl Ernst Schweigger and Wilhelm Uhthoff, leading to his interest in the subject and his writing his doctoral dissertation on it.

In 1890 he published an article with Kitasato Shibasaburō reporting that they had developed "antitoxins" against both diphtheria and tetanus. They had injected diphtheria and tetanus toxins into guinea pigs, goats and horses; when these animals developed immunity, they derived antitoxins (now known to contain antibodies) from their serum. This process would be called serum therapy by him at the time as he described it as a way to induce permanent immunity or "to stimulate the body's internal disinfection". These antitoxins could protect against and cure the diseases in non-immunized animals. In 1892 he started the first human trials of the diphtheria antitoxin, but they were unsuccessful. Successful treatment started in 1894, after the production and quantification of antitoxin had been optimized. During 1894, Behring was also awarded the Cameron Prize for Therapeutics of the University of Edinburgh.

In 1895 he became Professor of Hygienics within the Faculty of Medicine at the University of Marburg, a position held for the rest of his life. He and the pharmacologist Hans Horst Meyer had their laboratories in the same building, and Behring stimulated Meyer's interest in the mode of action of tetanus toxin.

Behring won the first Nobel Prize in Physiology or Medicine in 1901 for the development of serum therapies against diphtheria. His research colleague Kitasato Shibasaburō with whom together von Behring had laid the foundation for this therapy in 1890, while nominated as well, was not awarded the Nobel Prize.

Emil von Behring was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1902.

In 1904 he founded the Behringwerke in Marburg, a company to produce antitoxins and vaccines.