| Name | Source | Type | | Raas | Master of Orion III |
| Rabotevs | Harry Turtledove's Worldwar book series | A subject species of the Race in the Worldwar book series |
| The Race | Moreau series | Amoeboid |
| The Race | Harry Turtledove's Worldwar book series | Reptilian, often called "Lizards" by humans due to their appearance. |
| Rachni | Mass Effect |
| Raiel | Peter F. Hamilton's Pandora's Star |
| Rako-Gorda | Utopia |
| Ram Pythons | Battlelords of the 23rd Century |
| Rancors | Star Wars |
| Raptors | The Jupiter Incident |
| Raxacoricofallapatorians | Doctor Who |
| Reapers | Doctor Who |
| Reapers | Mass Effect |
| Reapers | UFO Defense |
| Regul | C. J. Cherryh's Alliance-Union universe |
| Relgarians | Farscape | Humanoid |
| Remans | Star Trek | Humanoid |
| Re'ol | Stargate SG-1 | Humanoid |
| Replicators | Stargate SG-1 | Artificial lifeform. Two variants are known to exist, in a small mechanical insect shape as well as full humanoid. |
| Re'tu | Stargate SG-1 |
| Rigellians | Lensman books | Barrel-shaped with four tentacular arms and four stubby legs |
| Rigellians (including Kang and Kodos) | The Simpsons |
| Riim | The Voyage of the Space Beagle by A. E. van Vogt |
| Rills | Doctor Who |
| Rimerunner | Expedition |
| Rimmer | Red Dwarf | Hologram-humanoid |
| Risa | Star Trek |
| Robotech Masters | Robotech |
| Rodians | Star Wars |
| Roger the Alien | American Dad! |
| Rogue Simulants | Red Dwarf | Humanoid |
| Romulans | Star Trek | Humanoid |
| Rull | The War against the Rull by A. E. van Vogt |
| Rutans | Doctor Who |
| Ryouko Asakura | The Melancholy of Haruhi Suzumiya | Humanoid interface |
| Ryqril | Timothy Zahn's The Blackcollar |