Fossil flowers and fruits of Archaefagacea futabensis gen. et sp. nov., from the Asamigawa Member of the Ashizawa Formation (early Coniacian) of the Futaba Group in northeastern Honshu, Japan, are described. Flowers are small and bisexual, with an inferior ovary and an epigynous perianth composed of six small triangular tepals. The androecium is composed of six stamens positioned opposite the tepals, and the gynoecium consists of a trilocular ovary with three persistent apical styles. A single seed may develop in one or more locules. Archaefagacea is linked to extant and fossil Fagales, including flowers of fossil Normapolles plants, by its floral structure. Archaefagacea provides the earliest evidence of floral structure among those Fagales (Fagaceae, Nothofagaceae, and extinct taxa) that fall outside the group of six extant families and related fossil Normapolles plants that constitute the core Fagales. It is also the first record of Fagales in the Late Cretaceous of eastern Eurasia.