Hans Christian Jacobaeus (29 May 1879 – 29 October 1937) was a Swedish internist born in Skarhult. In 1916 he became a professor at the Karolinska Institutet in Stockholm. From 1925 until his death in 1937, he was a member of the Nobel Prize Committee.
Jacobaeus was an important figure concerning modern laparoscopy and thoracoscopy. In 1910 he is credited with performing the first thoracoscopic diagnosis with a cystoscope. This technique was used in the treatment of a patient with tubercular intra-thoracic adhesions. In 1911 he published an article titled "The Possibilities for Performing Cystoscopy in Examinations of Serous Cavities" in the journal Münchner Medizinischen Wochenschrift.
He also did pioneer work involving cystoscopic diagnostics of the abdomen (laparoscopy). He understood the possibilities, as well as the limitations of this discipline, and was an advocate of endoscopic training for medical personnel. He also stressed the need for specialized instruments for optimum performance involving laparoscopic examinations.
In 1901 a Dresden physician named Georg Kelling (1866–1945) performed a cystoscope-aided intervention of a dog's abdomen. Kelling also claimed to have performed two successful laparoscopic examinations on humans prior to Jacobaeus, however Kelling failed to timely publish these experiences.
Hans Christian Jacobaeus was the father of Christian Jacobæus, a Swedish electrical engineer.