Walter Hohmann (no image available) (March 18, 1880 – March 11, 1945) was a German engineer who made an important contribution to the understanding of orbital dynamics. In a book published in 1925 (written in 1916), Hohmann demonstrated a very fuel-efficient path to move a spacecraft between two different orbits, now called a Hohmann transfer orbit.
Between 1911 and 1915, Hohmann devoted himself to the problem of interplanetary spaceflight, calculating the requirements of sending a spacecraft from Earth to one of the nearby planets of the Solar System. He realised that minimising the amount of fuel that the spacecraft had to carry would be an important consideration, and plotted a variety of orbits until he found the one that now bears his name. He published his findings in Die Erreichbarkeit der Himmelskörper (The Attainability of the Celestial Bodies). He was influenced in part by the German science fiction author Kurd Laßwitz and his book Auf Zwei Planeten.