Ludwig Louis Albert Zehnder (4 May 1854, Illnau – 24 March 1949, Oberhofen am Thunersee), Swiss physicist, inventor of an interferometer (See Mach–Zehnder interferometer).
Zehnder was a student of Wilhelm Röntgen, professor of physics at the universities of Freiburg and Basle. He produced the first pictures of the human skeleton by shining x-rays through the human body.