| Onthophagus lecontei Harold, 1871 |
| Onthophagus longecarinatus Zunino & Harold, 1988 |
| Onthophagus longimanus Bates, 1887 |
| Onthophagus luismargaritorum Delgado, 1995 |
| Onthophagus marginicollis Harold, 1880 |
| Onthophagus mariozuninoi Delgado & Navarrete-Heredia, 1993 |
| Onthophagus martinpierai Moctezuma, Rossini & Zunino, 2016 |
| Onthophagus mateui Moctezuma & Halffter, 2020 |
| Onthophagus maya Zunino, 1981 |
| Onthophagus mcclevei Howden & Génier, 2004 |
| Onthophagus mexicanus Bates, 1887 |
| Onthophagus mextexus Howden & Cartwright, 1970 |
| Onthophagus monticolus Howden & Cartwright, 1963 |
| Onthophagus moroni Zunino & Halffter, 1988 |
| Onthophagus mycetorum Zunino & Halffter, 1988 |
| Onthophagus nasicornis Guérin-Méneville, 1855 |
| Onthophagus navarretorum Delgado & Capistrán, 1996 |
| Onthophagus nemorivagus Kohlmann & Solís, 2001 |
| Onthophagus neofuscus Moctezuma & Halffter, 2020 |
| Onthophagus neomirabilis Howden, 1973 |