| Name | CR | Type | Environment |
| Nachzehrer | 12 | undead | any forest |
| Naga, Dark Naga | 8 | aberration | any underground |
| Naga, Deep Naga | 12 | aberration | any underground |
| Naga, Dream Naga | 9 | aberration (extraplanar) | any (Dimension of Dreams) |
| Naga, Guardian Naga | 10 | aberration | temperate plains |
| Naga, Lunar Naga | 6 | aberration | any land |
| Naga, Royal Naga | 11 | aberration (shapechanger) | any land |
| Naga, Slime Naga | 9 | aberration | any underground |
| Naga, Spirit Naga | 9 | aberration | temperate marshes |
| Naga, Water Naga | 7 | aberration (aquatic) | temperate water |
| Nagaji | 1/2 | humanoid (reptilian) | warm forests or hills |
| Naiad | 1/2 | fey (water) | any freshwater |
| Narrik | 7 | aberration | any underground |
| Necrocraft | 3 | undead | any land or underground |
| Necrophidius | 3 | construct | any |
| Neh-Thalggu | 8 | aberration | any |
| Nehushtan | 2 | magical beast | warm deserts and hills |
| Nekomata | 6 | magical beast (shapechanger) | any land |
| Nemhain | 15 | undead (incorporeal) | any |
| Neothelid | 15 | aberration | any underground |
| Neothelid Overlord | 20 | aberration | any underground |
| Nependis | 9 | monstrous humanoid | temperate forests |
| Nephilim | 8 | outsider (native) | warm hills |
| Nephlei | 9 | outsider (air, extraplanar) | any sky (Plane of Air) |
| Nereid | 10 | fey (water) | any aquatic |
| Neshmaal | 12 | outsider (extraplanar, incorporeal) | any |
| Ngoga | 7 | magical beast | warm jungles |
| Nightgaunt | 4 | monstrous humanoid (extraplanar) | any mountains (Dimension of Dreams) |
| Nightmare | 5 | outsider (evil, extraplanar) | any (Abaddon) |
| Nightmare Bats | 3 | outsider (evil, extraplanar) | Hell |
| Nightmare Creature, Nightmare Ettercap | 4 | aberration | temperate forests |
| Nightmare, Cauchemar | 11 | outsider (evil, extraplanar) | any (Abaddon) |
| Nightshade, Nightcrawler | 18 | undead (extraplanar, nightshade) | any (Negative Energy Plane) |
| Nightshade, Nightprowler | 10 | undead (extraplanar, nightshade) | any (Negative Energy Plane) |
| Nightshade, Nightwalker | 16 | undead (extraplanar, nightshade) | any (Negative Energy Plane) |
| Nightshade, Nightwave | 20 | undead (aquatic, extraplanar, nightshade) | any (Negative Energy Plane) |
| Nightshade, Nightwing | 14 | undead (extraplanar, nightshade) | any (Negative Energy Plane) |
| Nihiloi | 11 | outsider (extraplanar) | any (Plane of Shadow) |
| Nimbral Child | 11 | outsider (evil, extraplanar) | any land (Shadow Plane) |
| Ningen | 16 | monstrous humanoid | cold oceans |
| Ningyo | 1 | monstrous humanoid (aquatic) | warm oceans |
| Ningyo | 1 | monstrous humanoid (aquatic) | warm oceans |
| Ningyo, Undead Ningyo | 1 | undead (aquatic) | any aquatic or land |
| Nirento | 4 | plant | warm forests or plains |
| Nirento, Elder Nirento | 6 | plant | — |
| Nisid | 4 | fey | any island |
| Nixie | 1 | fey (aquatic) | temperate water |
| Nochlean | 3 | fey | temperate forests |
| Norn | 18 | fey | cold mountains |
| Nuckelavee | 9 | fey (aquatic) | cold swamps or coastlines |
| Nue | 10 | magical beast | warm forests or mountains |
| Nukkefeen | 1 | fey | any |
| Nulmind | 11 | plant | temperate forests |
| Nycar | 2 | dragon (aquatic) | cold marshes |
| Nymph | 7 | fey | temperate forest |