A new fossil lizard of the genus Pachygenys is described on the basis of a single, partially broken right mandible excavated from an unnamed formation of the Lower Cretaceous Sasayama Group in Hyogo Prefecture, western Honshu, Japan. The mandible exclusively shares a few apparently highly specialized morphological features, such as distinct foreshortening of the dentary tooth row and reduced dentary tooth number (nine), with Pachygenys thlastesa, the type species of the genus from the Lower Cretaceous of eastern China. However, the new species differs from the latter in having a shorter tooth row, anterior and middle teeth with unicuspid crowns (vs. bluntly truncated crowns in the latter), and posterior teeth with unicuspid and simple conical crowns (vs. bluntly truncated crowns in the latter). The specimen described here represents the first unequivocal fossil record of lizards in Japan, with its congeneric species occurring almost concurrently in eastern Eurasia.