| Onthophagus carpophilus Pereira & Halffter, 1961 |
| Onthophagus cartwrighti Howden, 1973 |
| Onthophagus cavernicollis Howden & Cartwright, 1963 |
| Onthophagus championi Bates, 1887 |
| Onthophagus chevrolati Harold, 1869 |
| Onthophagus chevrolati subsp. chevrolati Harold, 1869 |
| Onthophagus chevrolati subsp. longecarinatus Zunino & Halffter, 1988 |
| Onthophagus chevrolati subsp. omiltemius Zunino & Halffter, 1988 |
| Onthophagus chevrolati subsp. retusus Harold, 1869 |
| Onthophagus chiapanecus Zunino & Halffter, 1988 |
| Onthophagus chilapensis Gasca-Álvarez, Zunino & Deloya, 2018 |
| Onthophagus chimalapensis Delgado & Mora-Aguilar, 2019 |
| Onthophagus chinantecus Moctezuma & Halffter, 2019 |
| Onthophagus chryses Bates, 1887 |
| Onthophagus civitasorum Moctezuma & Halffter, 2020 |
| Onthophagus clavijeroi Moctezuma, Rossini & Zunino, 2016 |
| Onthophagus coahuilae Zunino & Halffter, 1988 |
| Onthophagus cochisus Brown, 1927 |
| Onthophagus coproides Horn, 1881 |
| Onthophagus corrosus Bates, 1887 |