| Orgyia falcata Schaus, 1896 |
| Orgyia pseudotsugata (McDunnough, 1921) |
| Orgyiini Wallengren, 1861 |
| Ormetica Clemens, 1861 |
| Ormetica ataenia (Schaus, 1910) |
| Ormetica nabdalsa (Schaus, 1889) |
| Ormetica orbona (Schaus, 1889) |
| Ormetica sicilia (Druce, 1884) |
| Ormetica taeniata (Guérin-Méneville, 1844) |
| Ormetica temperata (Schaus, 1921) |
| Orodesma Herrich-Schäffer, 1868 |
| Orodesma schausi (Druce, 1890) |
| Oruza Walker, 1861 |
| Osdara Walker, 1865 |
| Osdara ordinata Walker, 1865 |
| Oxidercia Hübner, 1825 [1816] |
| Oxidercia toxea (Stoll, 1781 [1782]) |
| Ozodania Dyar, 1899 |
| Ozodania subrufa Barnes & McDunnough, 1913 |
| Pachydota Hampson, 1901 |