| Name | Source | Type |
|---|---|---|
| Iberons | Imperium Galactica II: Alliances | |
| Ibs | Robert J. Sawyer's Starplex | |
| Ice Warriors | Doctor Who | humanoid |
| Iconians | Galactic Civilizations II: Dread Lords | |
| Iconians | Star Trek | |
| Ifshnit | Star Frontiers | Humanoid, meter-tall |
| Ikrini | Battlelords of the 23rd Century | |
| Ilanics | Farscape | Humanoid |
| Ilwrath | Star Control | Spider-like |
| Impostors | Among Us | |
| Imsaeis | Master of Orion | |
| Imskians | DC Comics' Legion of Super-Heroes | |
| Ing | Metroid Prime 2: Echoes | Beings native to a dark mirror dimension. Some can change into forms relating to solid, liquid, and gaseous states. They have the ability to possess and corrupt both living and dead creatures. Main enemy to Luminoth. |
| Insects | The History of the Galaxy series | |
| Interions | Farscape | Humanoid |
| Interplanet Janet | Schoolhouse Rock! | |
| Invid/Inbit | Robotech: The New Generation and their counterparts from Genesis Climber Mospeada | crab-like |
| Irkens | Invader Zim | Green humanoids (usually small) with an appetite for destruction |
| Isanians | Perry Rhodan | |
| Ishtarians | Poul Anderson's Fire Time | |
| Ithanites | Star Trek | |
| Ithkul | Master of Orion III | |
| Ixtl | The Voyage of the Space Beagle by A. E. van Vogt |