| Ochetodon Coues, 1874 |
| Ochetodon mexicanus (Saussure, 1860) |
| Ochetodon mexicanus subsp. mexicanus (Saussure, 1860) |
| Ochetodon montanus (Baird, 1855) |
| Ochetodon sumichrasti (Saussure, 1861) |
| Ochrotomyini |
| Oligoryzomys Bangs, 1900 |
| Oligoryzomys fulvescens (Saussure, 1860) |
| Oligoryzomys fulvescens subsp. engraciae (Osgood, 1945) |
| Oligoryzomys fulvescens subsp. fulvescens (Saussure, 1860) |
| Oligoryzomys fulvescens subsp. lenis (Goldman, 1915) |
| Oligoryzomys fulvescens subsp. mayensis (Goldman, 1918) |
| Oligoryzomys fulvescens subsp. pacificus (Hooper, 1952) |
| Ondatra Link, 1795 |
| Ondatra zibethicus (Linnaeus, 1766) |
| Ondatra zibethicus subsp. bernardi Goldman, 1932 |
| Ondatra zibethicus subsp. ripensis (Bailey, 1902) |
| Ondatrini |
| Onychomys Baird, 1858 |
| Onychomys arenicola Mearns, 1896 |