| Onychomys torridus subsp. ramona Rhoads, 1893 |
| Onychomys torridus subsp. surrufus Hollister, 1914 |
| Onychomys torridus subsp. torridus (Coues, 1874) |
| Onychomys torridus subsp. yakiensis Merriam, 1904 |
| Orthriomys Merriam, 1898 |
| Orthriomys umbrosus (Merriam, 1898) |
| Oryzomyini |
| Oryzomys Baird, 1858 |
| Oryzomys albiventer Merriam, 1901 |
| Oryzomys alfaroi (J. A. Allen, 1891) |
| Oryzomys alfaroi subsp. agrestis Goodwin, 1959 |
| Oryzomys alfaroi subsp. angusticeps Merriam, 1901 |
| Oryzomys alfaroi subsp. caudatus Merriam, 1901 |
| Oryzomys alfaroi subsp. chapmani Thomas, 1898 |
| Oryzomys alfaroi subsp. dilutior Merriam, 1901 |
| Oryzomys alfaroi subsp. gloriaensis Goodwin, 1956 |
| Oryzomys alfaroi subsp. guerrerensis Goldman, 1915 |
| Oryzomys alfaroi subsp. huastecae Dalquest, 1951 |
| Oryzomys alfaroi subsp. hylocetes Merriam, 1901 |
| Oryzomys alfaroi subsp. palatinus Merriam, 1901 |