The new species Groenlandia pescheri D. Uhl & Poschmann sp. nov., belonging to the family Potamogetonaceae, is described from the Late Oligocene Fossil-Lagerstätte Enspel (Westerwald, Germany). The species is characterized by sub-oppositely arranged leaves without observable stipule-like appendages at the leaf bases and a very thin exocarp (both characteristics of the aquatic genus Groenlandia J. Gay) with a spiked crest (which differs from the only other species included in this genus, the modern Groenlandia densa (L.) Four.). The taxon represents the first pre-Quaternary record of the genus Groenlandia, which is usually regarded as a basal sister group of all other Potamogetonaceae.