Julius Isidor Rosenthal (16 July 1836 – 2 January 1915) was a German physiologist who was a native of Labischin.
In 1859 he received his doctorate from the University of Berlin, where he was a student of Emil du Bois-Reymond (1818-1896). Afterwards he remained in Berlin as an assistant at the institute of physiology, where in 1867 he became an assistant professor. In 1872 he was appointed professor of physiology at the University of Erlangen.
Rosenthal made contributions in the physiological research of respiration, and in investigations of heat regulation in warm-blooded animals.
He was the author of several articles in Ludimar Hermann's Lehrbuch der Physiologie, and in 1881 became editor of the scientific journal Biologisches Zentralblatt. His book Allgemeine Physiologie der Muskeln und Nerven (General Physiology of Muscles and Nerves) was later translated into English.