Johannes Orth (14 January 1847 – 13 January 1923 in Berlin) was a German pathologist born in Wallmerod. He studied medicine at the universities of Heidelberg, Würzburg and Bonn, receiving his habilitation in 1872 while an assistant to Eduard von Rindfleisch at Bonn. Afterwards, he served as an assistant under Rudolf Virchow (1821-1902) in Berlin. In 1878 he became a professor at the University of Göttingen, and in 1902, following the death of Virchow, he returned to Berlin as director of the clinic of pathology.