| Name | Source | Type | |
|---|---|---|---|
| Iberons | |||
| Robert J. Sawyer's Starplex | |||
| Ice Warriors | Doctor Who | humanoid | |
| Iconians | |||
| Iconians | Star Trek | ||
| Star Frontiers | Humanoid, meter-tall | ||
| Battlelords of the 23rd Century | |||
| Ilanics | Farscape | Humanoid | |
| Star Control | Spider-like | ||
| Impostors | Among Us | ||
| Imsaeis | Master of Orion | ||
| Imskians | |||
| 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! | ||
| Robotech: The New Generation and their counterparts from Genesis Climber Mospeada | crab-like | ||
| 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 |