Emil Theodor Kocher (25 August 1841 – 27 July 1917) was a Swiss physician, medical researcher, and Nobel laureate for his work in the physiology, pathology and surgery of the thyroid.

Kocher was born in Bern, Switzerland. He studied in Zürich, Berlin, London and Vienna, and obtained his doctorate in Bern in 1865. In 1872, he succeeded Georg Albert Lücke as Ordinary Professor of Surgery and Director of the University Surgical Clinic at the Inselspital in Bern. He published works on a number of subjects other than the thyroid gland including hemostasis, antiseptic treatments, surgical infectious diseases, on gunshot wounds, acute osteomyelitis, the theory of strangulated hernia, and abdominal surgery. His new ideas on the thyroid gland were initially controversial but his successful treatment of goiter with a steadily decreasing mortality rate soon won him recognition. The prize money, from the Nobel prize he received, helped him to establish the Kocher Institute in Bern.

A number of instruments (for example the craniometer) and surgical techniques (for example, the Kocher manoeuvre, and Kocher incision) are named after him, as well as the Kocher - Debre - Semelaigne syndrome.