Njoerdichthys is an extinct genus of pycnodontid fish from the Cretaceous Hesseltal Formation in Germany.

[1] The original holotype of Njoerdichthys was discovered in 1995 at the abandoned Galgenknapp quarry, previously owned by the Dyckerhoff AG company, while the paratype specimens were discovered in the Hohne quarry, also owned by the company, located west of Lengerich, Germany.

Despite lacking a postparietal process, phylogenetic analysis still finds it a part of the Pycnodontidae family, in the Nursalliinae subfamily.

[1] Njoerdichthys is the most northerly pycnodontiform recorded from the Cretaceous, living in a marine environment during the early Turonian, when temperatures peaked their highest during the Mesozoic.

This, with the discovery of Anomoedus in Sweden, is additional evidence to pycnodontids having expanded into higher latitudes with the warming of the climate and that climate played a crucial role in their expansion.