| Name | CR | Type | Environment |
| Umbracygot | 12 | aberration | any (terrestrial vacuum) |
| Undead Minion, Cybernetic Zombie | 3 | undead | any |
| Undead Minion, Occult Zombie | 1 | undead | any |
| Undead Minion, Skeletal Undead | 1/2 | undead | any |
| Undershrike | 5 | aberration | any underground (Absalom Station) |
| Urog | 3 | magical beast | warm hills and mountains (Dykon) |
| Ursikka | 10 | magical beast | any arctic (Triaxus) |
| Ursine Horror | 9 | outsider (chaotic, evil, extraplanar, incorporeal) | any vacuum |
| Ursolha | 15 | aberration | any |
| Utesra, Phylarch | 11 | vermin | any hill, mountain, or urban |
| Utesra | 5 | vermin | any hill, mountain, or urban |