The genus Syzygium (Myrtaceae) is revised for Indochina (Cambodia, Laos and Vietnam). The species key, descriptions, typification, ecology, conservation status, phenology, vernacular names, usages, distribution maps, selected herbarium images and list of specimens examined are given. A total of fifty-six species are recognised in Indochina. Eight species including Syzygium bokorense W.K.Soh & J.Parn., S. chantaranothaianum W.K.Soh & J.Parn., S. crassiflorum Merr. & L.M.Perry, S. cucphuongense W.K.Soh & J.Parn., S. glomerulatum (Gagnep.) Merr. & L.M.Perry, S. harmandii (Gagnep.) Merr. & L.M.Perry, S. pierrei (Gagnep.) Merr. & L.M.Perry and S. tonkinense (Gagnep.) Merr. & L.M.Perry are confined to Indochina. 63 lectotypes were designated and 23 previously accepted species names are now synonyms under Syzygium. Vietnam harbours the largest number of species (49), followed by Laos (30) and Cambodia (27). Syzygium attopeuense (Gagnep.) Merr. & L.M.Perry and Syzygium corticosum (Lour.) Merr. & L.M.Perry are new records for Thailand.