| Otatea victoriae Ruiz-Sanchez, 2015 |
| Otatea ximenae Ruiz-Sanchez & L.G. Clark, 2011 |
| Ottochloa Dandy, 1931 |
| Ottochloa malabarica (L.) Dandy, 1931 |
| Oxyanthe Steud., 1855 |
| Oxyanthe phragmites (L.) Nieuwl., 1914 |
| Oxydenia Nutt., 1818 |
| Padia Moritzi, 1845 |
| Pallasia Scop., 1777 |
| Paneion Lunell, 1915 |
| Paneion compressum (L.) Lunell, 1915 |
| Paneion longiligulum (Scribn. & T.A. Williams) Lunell, 1915 |
| Paneion nemorale (L.) Lunell, 1915 |
| Paneion pratense (L.) Lunell, 1915 |
| Paneion sandbergii (Vasey) Lunell, 1915 |
| Paniceae R. Br., 1814 |
| Panicinae Fr., 1835 |
| Panicoideae A. Braun, 1864 |
| Panicularia Heist. ex Fabr., 1759 |
| Panicum L., 1753 |