The Late Paleocene locality of Louvois is located about 20 km south of Reims, in the department of Marne (France). These marly sediments have yielded numerous vertebrate remains. The Louvois fauna is coeval with those of the localities of Cernay-les-Reims and Berru and is dated as reference-level MP6, late Thanetian. Here we provide a detailed description of the remains of giant flightless gastornithids that were preliminarily reported in a study of the vertebrate fauna from Louvois. These fragmentary gastornithid remains mainly include a carpometacarpus, several tarsometatarsi, and numerous pedal phalanges. These new avian fossils add to the fossil record of Gastornis, which has been reported from various Early Paleogene localities in the Northern Hemisphere. Tarsometatarsi and pedal phalanges show large differences in size, which may be interpreted as sexual size dimorphism. The specimens from Louvois are morphologically different from those of Gastornis parisiensis and G. russelli, from Cernay and Berru. The Louvois carpometacarpus is also different from that of the North American G. giganteus, and the Louvois pedal phalanges are shorter and stouter than in other species of Gastornis. Moreover, the Louvois tarsometatarsi are more similar to that of the much younger G. sarasini, from Monthelon, reference-level MP 10, late Ypresian. We refrain from assigning the Louvois specimens to a new species of Gastornis and we designate it as Gastornis sp., owing to the fragmentary nature of the material. However, the morphological features of the Louvois material are sufficiently distinct for us to propose that three different forms of Gastornis were present in the Late Paleocene of North-eastern France.