A new enantiornithine bird, Bohaiornis guoi, gen. et sp. nov., is described in this paper. The holotype, presumably a sub-adult, is a complete, fully articulated skeleton from the Lower Cretaceous Yixian Formation of western Liaoning, northeastern China. Bohaiornis exhibits some similarity in morphology to Eoenantiornis, but Bohaiornis is much larger than Eoenantiornis and differs from all previously known enantiornithine birds including Eoenantiornis in having the following features: caudal end of the articular pointed caudoventrally, sacral centra strongly compressed transversely, and clavicular ramus straight with a laterally expanded omal end. The almost perfectly preserved skeleton of this new specimen not only reveals many morphological features previously unknown in basal birds, but also clarifies many fine details of previously known features.