| Orizabus ligyroides Horn, 1885 |
| Orizabus parvitarsis Casey, 1915 |
| Orizabus ponderosus Casey, 1915 |
| Orizabus pyriformis LeConte, 1848 |
| Orizabus rawlinsi Dechambre, 1993 |
| Orizabus rubricollis Prell, 1914 |
| Orizabus snowi Horn, 1885 |
| Orizabus subaziro Ratcliffe, 1994 |
| Orizabus tuberculatus Prell, 1914 |
| Orizabus vulcanicus Morón, Tapia & Aragón, 2003 |
| Orphninae Erichson, 1847 |
| Oryctes Illiger, 1798 |
| Oryctes rhinoceros (Linnaeus, 1758) |
| Oryctini Mulsant, 1842 |
| Otophorus Mulsant, 1842 |
| Otophorus haemorrhoidalis (Linnaeus, 1758) |
| Oxygrylius Casey, 1915 |
| Oxygrylius pimalis Casey, 1915 |
| Oxygrylius ruginasus LeConte, 1856 |
| Oxyomus Dejean, 1833 |