Ohmdenia is an extinct genus of prehistoric bony fish that lived from the Toarcian stage of the Early Jurassic period. Ohmdenia was first described in 1953 by Bernhard Hauff, based on a fossil found in the well-known Posidonia Shale in Holzmaden, Germany. For a long time this animal has been considered a close relative of Birgeria, a great predator typical of the Triassic period with an uncertain systematic position. Further studies have shown similarities with the Pachycormiformes, a group considered close to the origin of teleosts and also including giant forms and planktivores. Some studies have erroneously indicated Ohmdenia as a synonym of Saurostomus, other studies have instead placed Ohmdenia as an important evolutionary link between the basal pachycormiforms and the more derived planktivore pachycormiformes.