List of fictional alien species: U
| Name | Source | Type |
|---|---|---|
| Ul-Mor | Star Frontiers | Nomadic land octopuses |
| Umgah | Star Control | |
| Unas | Stargate SG-1 | |
| Uncle of the Ramen Shop | Taro the Space Alien | an alien who cooks ramen has three daughters |
| Uncreated | Marvel Comics | |
| Unggoy | Halo | |
| Ungooma | Ascendancy | |
| Uniocs | Schlock Mercenary | |
| Unity | Superman: The Animated Series | |
| Ur-Quan Kohr-Ah | Star Control | |
| Ur-Quan Kzer-Za | Star Control | |
| Urpneys | The Dreamstone | |
| U'tani | Star Trek | |
| Utrom | Teenage Mutant Ninja Turtles | |
| Utwig | Star Control | Humanoid |
| Uxorite | Ben 10 |