| Opius microscopicus Fisher, 1963 |
| Opius mitiformis Fisher, 1964 |
| Opius mitis Fisher, 1963 |
| Opius nympha Fisher, 1968 |
| Opius oaxacanus Fischer, 1964 |
| Opius oophilus Fullaway, 1951 |
| Opius orizabensis Fisher, 1963 |
| Opius parkercreekensis Fischer, 1964 |
| Opius signicoxa Fisher, 1969 |
| Opius simillimus Fisher, 1964 |
| Opius superficiarius Fisher, 1969 |
| Opius terebrifer Fisher, 1968 |
| Opius tergitalis Fisher, 1966 |
| Opius tolucaensis Fisher, 1968 |
| Opius zacapuensis Fisher, 1964 |
| Oresimus Ashmead, 1900 |
| Orgilinae Achterberg, 1998 |
| Orgilini |
| Orgilomorpha Ashmead, 1900 |
| Orgilus Haliday, 1833 |