Friedrich Wilhelm Zahn (14 February 1845 – 1904) was a German-Swiss pathologist born in Germersheim. His eponyms include Zahn infarct and lines of Zahn.
Zahn studied medicine at the University of Strasbourg under Friedrich Daniel von Recklinghausen (1833–1910), becoming an associate professor of pathological anatomy in Geneva in 1876.
Zahn published works on the circulatory system (blood, thrombosis, embolism, arterial disease, etc.) and on tumors. With Georg Albert Lücke (1829–1894), he published an influential treatise involving surgery of tumors, Chirurgie der Geschwülste. Other noted writings by Zahn include: