The archaic cynipoid family Ibaliidae is revised. All described taxa are included in a checklist, and keys to valid taxa are presented. Host records include larvae of several woodwasp species (Siricidae: Siricinae and Tremicinae). Ibaliidae is considered to include the East Asian genus Heteribalia Sakagami, with five valid species, and the mainly Holarctic genus Ibalia Latreille, with 13 valid species, seven in the subgenus Ibalia and six in the subgenus Tremibalia. Heteribalia aureopilosa Maa, 1949 and H. subtilis Maa, 1949 are raised from subspecies to species level. Ibalia (T.) hunanica sp. n., is described from Oriental China. Three morphs of I. (T.) anceps, differing in wing colour pattern, are recognized, and distribution records of these morphs in North America are mapped. I. scalpellator Westwood, 1837 is synonymized with I. anceps Say, 1824; I. takaehihoi Yasumatsu, 1937 with I. jakowlewi Jacobson, 1899; I.fulviceras Yang, 1991 with I. ornata Belizin, 1968; and I. yunshae Yang et Liu,1992 with I. rufipes drewseni Borries, 1891. Lectotypes are designated for I. picea Matsumura, 1912 (syn. of I. leucospoides (Hochenwarth, 1785)) and for I. japonica Matsumura, 1912.