Otto Ernst Küstner (26 August 1849, Trossin, Province of Saxony – 12 May 1931) was a German gynecologist. Initially he studied medicine in Leipzig and Berlin, and during the Franco-Prussian War was a volunteer with the Garde-Füsilier-Regiment. Afterwards, he continued his studies at the University of Halle, obtaining his doctorate in 1873. He then furthered his education in Vienna, later returning to Halle as an assistant in the polyclinic of Theodor Weber and also in the obstetrics institute under Robert Michaelis von Olshausen.