Nautilus praepompilius is an extinct species of nautilus. It lived during the Late Eocene through Oligocene epochs. Fossil specimens have been uncovered from the Chegan Formation of Kazakhstan. N. praepompilius has been grouped into a single taxon together with extant species based on their shared shell characters. It is morphologically closest to N. pompilius, hence the name. The nepionic constriction shows that the hatching size was approximately 23 mm, close to that for N. pompilius. N. praepompilius, along with aff. N. cookanum fossils from the late Eocene Hoko River Formation in Washington state are the oldest occurrences of the genus.