A new fossil stephanid wasp (Stephanidae, or so called ‘crown wasps’) is described and figured from mid-Cretaceous Burmese amber. Kronostephanus zigrasi Engel and Grimaldi, new genus and species, is the oldest stephanid currently known in amber, and only the second amber specimen documented from the Mesozoic. Like Archaeostephanus corae Engel and Grimaldi (Turonian, New Jersey), the Burmese species belongs to the basal subfamily Schlettereriinae. The implications of this new taxon are elaborated and comments are provided regarding the age of the clade as well as the Hymenoptera as a whole.