Erwin Otto Eduard von Bälz (German pronunciation: [ˈɛʁviːn ˈɔto ˈeːduaʁt fɔn ˈbɛlt͡s]; 13 January 1849 – 31 August 1913), often simply known as Erwin Bälz without the noble "von" particle, was a German internist, anthropologist, and personal physician to the Japanese Imperial Family and cofounder of modern western medicine in Japan.

Bälz’s contract was renewed several times, and he ended up spending 27 years in Japan, the longest of any of the Oyatoi gaikokujin advisors.

During his stay in Japan, he tried to promote sports activity among the students of the Tokyo University, recommending unsuccessfully to revive the practice of jujutsu and kenjutsu.

During his stay in Japan, he treated some of the most influential men in the Meiji government, including Prime Ministers Itō Hirobumi and Yamagata Aritomo.

He compared the area with the European spa resort of Karlsbad, and felt that mountainous air, as well as the clear waters, was very conducive to health.

Bälz was also an ardent art collector; the majority of the Japanese works collected by him are located at the Linden Museum in Stuttgart.