| Name | CR | Type | Environment |
| Radiation Drake, Adult | 9 | dragon | any land |
| Radiation Drake, Slasher | 4 | dragon | any land |
| Rageshkor, Green | 6 | animal | temperate or warm forests or plains |
| Rageshkor, Rock | 12 | animal | any deserts or mountains |
| Rauzhant | 6 | dragon | any air (Liavara) |
| Ravai | 6 | fey (fire) | any solar |
| Ravenous Drake, Domesticated | 1/2 | dragon | temperate forests |
| Ravenous Drake, Feral | 2 | dragon | temperate forests |
| Ravenous Skull | 1 | undead | any |
| Ravenous Skull, Ravenous Skull Swarm | 6 | undead (swarm) | any |
| Raxilite, Raxilite Bioengineer | 4 | plant | any (Raxil) |
| Raxilite, Raxilite Researcher | 1/2 | plant | any (Raxil) |
| Razordoll | 7 | undead (android) | any urban |
| Rebuilt | 7 | aberration | any ruins (Nejeor VI) |
| Reflection | 8 | outsider (elemental, extraplanar, water) | any aquatic |
| Reklan | 7 | magical beast | any (Diaspora) |
| Religious Figures, Champion | 14 | monstrous humanoid | — |
| Religious Figures, Divine Avatar | 20 | humanoid (vlaka) | — |
| Religious Figures, Excommunicant | 4 | humanoid (ryphorian) | — |
| Religious Figures, Prophet | 8 | aberration | — |
| Rendalairn | 25 | construct (magical) | any |
| Renkroda, Whiskered | 5 | animal | temperate or warm forests (Castrovel) |
| Renkroda, Whiskered Renkroda | 5 | animal | temperate or warm forests (Castrovel) |
| Replicant Ooze | 7 | ooze (shapechanger) | any |
| Reptoid Hybrid | 8 | humanoid (kasatha, reptoid) | any |
| Reptoid | 1 | humanoid (reptoid, shapechanger) | any |
| Reptoid, Reptoid Master | 6 | humanoid (reptoid, shapechanger) | any |
| Rheonnaghan | 15 | outsider (native) | vacuum |
| Rift Stinger | 19 | construct (technological) | — |
| Riftstalker | 8 | outsider (chaotic, extraplanar) | any |
| Robot (Security), Luminance-class Security Robot | 5 | construct (technological) | any urban |
| Robot (Security), Observer-Class Security Robot | 1 | construct (technological) | any urban |
| Robot (Security), Patrol-Class Security Robot | 4 | construct (technological) | any urban |
| Robot Dragon, Assault Disintegrator Dragon | 16 | dragon (technological) | any |
| Robot Dragon, Assault Laser Dragon | 12 | dragon (technological) | any |
| Robot, Assassin Robot | 9 | construct (technological) | any |
| Robot, Azlanti Adjutant | 3 | construct (magical) | any (Azlanti Star Empire) |
| Robot, Azlanti Battle Robot | 6 | construct (technological) | any urban (Azlanti Star Empire) |
| Robot, Guardian Robot | 5 | construct (technological) | any |
| Robot, Incapacitator | 3 | construct (technological) | any |
| Robot, Keeper Robot | 18 | construct (technological) | any land |
| Robot, Mining | 9 | construct (technological) | any underground |
| Robot, Siege Robot | 15 | construct (technological) | any |
| Robot, Terminator-Class Security | 10 | construct (technological) | any urban |
| Rogue Drone, Rogue Combat Drone | 14 | construct (technological) | any |
| Rogue Drone, Rogue Hover Drone | 6 | construct (technological) | any |
| Ryphorian, Ryphorian Skyfire Pilot | 5 | humanoid (ryphorian) | any (Triaxus) |
| Ryphorian, Ryphorian Technician | 1 | humanoid (ryphorian) | any (Triaxus) |