We report the discovery of Erenlagus anielae, a new genus and species of stem lagomorph from the lower part of the Middle Eocene Irdin Manha Formation at the Huheboerhe locality, Erlian Basin, Nei Mongol, China. The remains consist of isolated teeth; however, the material includes all loci except the incisors and P2. The new lagomorph is characterized by a small size and high degree of unilateral hypsodonty comparable to that of Aktashmys and slightly higher than that observed in the coeval and co-occurring Strenulagus. Further, it shows advanced root fusion, which exceeds even that in Gobiolagus. Although phylogenetic relationships of the Eocene lagomorphs from Asia are still not fully resolved, the dental characters of Erenlagus anielae suggest that it is most closely related to Lushilagus danjingensis from the Middle Eocene of Henan, China and Aktashmys montealbus from the late Early Eocene of Kyrgyzstan. This stratigraphically well-constrained finding represents one of the lagomorph genera that appeared in the Eocene Glires paleobiodiversity reservoir, the Erlian Basin in Nei Mongol.