| Agrostis owariensis Roem. & Schult., 1824 |
| Agrostis pallens Trin., 1841 |
| Agrostis pallens var. foliosa Hitchc., 1905 |
| Agrostis pallens var. vaseyi H. St. John, 1937 |
| Agrostis palustris Huds., 1762 |
| Agrostis panicea Lam., 1783 |
| Agrostis patula Gaudin, 1808 |
| Agrostis pauciflora Pursh, 1814 |
| Agrostis perennans (Walter) Tuck., 1843 |
| Agrostis perennans var. elata (Pursh) HItchc., 1905 |
| Agrostis perennans var. estivalis Vasey, 1892 |
| Agrostis perennans var. humilis Farw., 1923 |
| Agrostis peruviana (P. Beauv.) Spreng., 1824 |
| Agrostis pickeringii Tuck., 1843 |
| Agrostis pickeringii var. rupicola Tuck., 1843 |
| Agrostis plumosa Ten., 1811 |
| Agrostis poeppigiana Phil., 1896 |
| Agrostis poiformis Willd. ex Steud., 1840 |
| Agrostis polydactyla Salzm. ex Döll, 1877 |
| Agrostis polymorpha Huds., 1778 |