Ellimmichthys is an extinct genus of freshwater clupeomorph fish belonging to the order Ellimmichthyiformes, of which it is the type genus. It was a distant relative of modern herrings and anchovies. It inhabited freshwater rift lakes in the supercontinent of West Gondwana (comprising modern South America and Africa) during the Early Cretaceous, and fossil remains are known from formations in both South America (Brazil) and Africa (Equatorial Guinea).
The following species are known:
Another species E. maceioensis <small>Malabarba et al, 2004</small> from the Aptian-aged Maceió Formation of Alagoas, Brazil likely does not belong to this genus as it does not display diagnostic morphological characteristics. However, the genus as a whole may also be paraphyletic with respect to Ellimma.
The sister genus to Ellimmichthys is thought to be Eoellimmichthys, a marine paraclupeid that lived much later during the Early Eocene, with fossils known from Monte Bolca, Italy. Eoellimmichthys is thought to have been the last surviving paraclupeid, and the last surviving marine ellimmichthyiform as a whole.