Rhysacephala masneri sp. n. (Hymenoptera, Xiphydriidae), the first symphytan recorded from Lord Howe Island is described. Xiphydriid woodwasps are rarely collected in Australasia and the distribution of Rhysacephala, which is known from only seven described species from eastern Australia, New Guinea and New Caledonia, is significantly extended. We also discuss putative relationships among Australasian members of the genus.