| porcine respiratory coronavirus | 34 | no rank | viruses | viruses | 11146 |
| porcine rotavirus a | 2 | no rank | viruses | viruses | 10967 |
| porphyromonas | 106 | genus | bacteria | | 836 |
| porphyromonas asaccharolytica | 22 | species | bacteria | bacteria | 28123 |
| porphyromonas catoniae | 6 | species | bacteria | bacteria | 41976 |
| porphyromonas circumdentaria | 7 | species | bacteria | bacteria | 29524 |
| porphyromonas endodontalis | 27 | species | bacteria | bacteria | 28124 |
| porphyromonas gingivalis | 113 | species | bacteria | bacteria | 837 |
| porphyromonas levii | 12 | species | bacteria | bacteria | 28114 |
| porphyromonas macacae | 16 | species | bacteria | bacteria | 28115 |
| porrocaecum angusticolle | 4 | species | invertebrates | helminths | 290550 |
| porrocaecum aridae | -3 | species | | helminths | |
| porrocaecum crassum | -3 | species | invertebrates | helminths | 290549 |
| porrocaecum depressum | 1 | species | invertebrates | helminths | 59262 |
| postharmostomum commutatus | -3 | species | | helminths | |
| postharmostomum suis | -3 | species | | helminths | |
| posthodiplostomum cuticula | 1 | species | | helminths | |
| posthodiplostomum minimum | 14 | species | invertebrates | helminths | 57260 |
| powassan virus | 11 | species | viruses | viruses | 11083 |
| prevotella | 78 | genus | bacteria | | 838 |
| prevotella bivia | 20 | species | bacteria | bacteria | 28125 |
| prevotella buccae | 17 | species | bacteria | bacteria | 28126 |
| prevotella buccalis | 4 | species | bacteria | bacteria | 28127 |
| prevotella corporis | 6 | species | bacteria | bacteria | 28128 |
| prevotella dentalis | 7 | species | bacteria | bacteria | 52227 |
| prevotella denticola | 18 | species | bacteria | bacteria | 28129 |
| prevotella disiens | 8 | species | bacteria | bacteria | 28130 |
| prevotella enoeca | 2 | species | bacteria | bacteria | 76123 |
| prevotella intermedia | 65 | species | bacteria | bacteria | 28131 |
| prevotella loescheii | 21 | species | bacteria | bacteria | 840 |
| prevotella melaninogenica | 28 | species | bacteria | bacteria | 28132 |
| prevotella nigrescens | 37 | species | bacteria | bacteria | 28133 |
| prevotella oralis | 18 | species | bacteria | bacteria | 28134 |
| prevotella oris | 13 | species | bacteria | bacteria | 28135 |
| prevotella oulorum | 4 | species | bacteria | bacteria | 28136 |
| prevotella ruminicola | 39 | species | bacteria | bacteria | 839 |
| prevotella veroralis | 7 | species | bacteria | bacteria | 28137 |
| procerovum calderoni | 1 | species | | helminths | |
| prohemistomum vivax | 1 | species | | helminths | |
| propionibacterium | 87 | genus | bacteria | | 1743 |
| propionibacterium acnes | 77 | species | bacteria | bacteria | 1747 |
| propionibacterium avidum | 11 | species | bacteria | bacteria | 33010 |
| propionibacterium granulosum | 18 | species | bacteria | bacteria | 33011 |
| propionibacterium propionicum | 18 | species | bacteria | bacteria | 1750 |
| propionigenium | 38 | genus | bacteria | | 2332 |
| prosarcoptes allenopitheci | -3 | species | | | |
| prosarcoptes faini | -3 | species | | | |
| prosarcoptes pitheci | -3 | species | | | |
| prosthenorchis elegans | 3 | species | | helminths | 1781191 |
| prosthenorchis spicula | -3 | species | | helminths | |
| prosthodendrium molenkampi | 5 | species | | helminths | |
| prosthogonimus anatinus | -3 | species | | helminths | |
| prosthogonimus cuneatus | 1 | species | invertebrates | helminths | 232414 |
| prosthogonimus macrorchis | 1 | species | | helminths | |
| prosthogonimus ovatus | 1 | species | invertebrates | helminths | 99714 |
| prosthogonimus oviformis | -3 | species | | helminths | |
| proteocephalus ambloplitis | 9 | species | invertebrates | helminths | 100446 |
| proteus | 99 | genus | bacteria | | 583 |
| proteus mirabilis | 80 | species | bacteria | bacteria | 584 |
| proteus penneri | 16 | species | bacteria | bacteria | 102862 |
| proteus vulgaris | 53 | species | bacteria | bacteria | 585 |
| protophormia terraenovae | 43 | species | invertebrates | fly | 34676 |
| protostrongylus brevispiculum | 2 | species | | helminths | |
| protostrongylus davtiani | -3 | species | | helminths | |
| protostrongylus hobmaieri | 1 | species | | helminths | 1418101 |
| protostrongylus oryctolagi | -3 | species | | helminths | 1519148 |
| protostrongylus rufescens | 7 | species | invertebrates | helminths | 321386 |
| protostrongylus skrjabini | -3 | species | | helminths | |
| protostrongylus stilesi | 8 | species | invertebrates | helminths | 473978 |
| protostrongylus sylvilagi | -3 | species | | helminths | |
| protostrongylus tauricus | 1 | species | | helminths | |
| prototheca wickerhamii | 26 | species | plants | | 3111 |
| prototheca zopfii | 23 | species | plants | | 3112 |
| providencia | 50 | genus | bacteria | | 586 |
| providencia alcalifaciens | 15 | species | bacteria | bacteria | 126385 |
| providencia rettgeri | 31 | species | bacteria | bacteria | 587 |
| providencia stuartii | 41 | species | bacteria | bacteria | 588 |
| pseudamphistomum aethiopicum | -3 | species | | helminths | |
| pseudamphistomum truncatum | 5 | species | invertebrates | helminths | 524295 |
| pseudoalteromonas | 48 | genus | bacteria | | 53246 |
| pseudocowpox virus | 10 | species | viruses | viruses | 129726 |
| pseudodiscus collinsi | -3 | species | | helminths | |
| pseudomonas | 295 | genus | bacteria | | 286 |
| pseudomonas aeruginosa | 243 | species | bacteria | bacteria | 287 |
| pseudomonas alcaligenes | 25 | species | bacteria | bacteria | 43263 |
| pseudomonas fluorescens | 122 | species | bacteria | bacteria | 294 |
| pseudomonas pseudoalcaligenes | 41 | species | bacteria | bacteria | 330 |
| pseudomonas putida | 133 | species | bacteria | bacteria | 303 |
| pseudomonas stutzeri | 76 | species | bacteria | bacteria | 316 |
| pseudonocardia autotrophica | 10 | species | bacteria | bacteria | 2074 |
| pseudoramibacter | 11 | genus | bacteria | | 113286 |
| pseudoramibacter alactolyticus | 13 | species | bacteria | bacteria | 113287 |
| pseudoterranova | 26 | genus | invertebrates | | 6270 |
| pseudoterranova decipiens | 28 | species | invertebrates | helminths | 6271 |
| psilorchis hominis | -3 | species | | helminths | |
| psittacid herpesvirus 1 | 5 | species | viruses | viruses | 50294 |
| psittacid herpesvirus 2 | 3 | species | viruses | viruses | 240874 |
| psittacid herpesvirus 3 | -3 | species | viruses | viruses | 240876 |
| psittacid herpesvirus 4 | -3 | species | viruses | viruses | 240877 |
| psorergates bos | 1 | species | | | |