| Name | Source | Type | |
|---|---|---|---|
| Y5 | Rabbit-like humanoid | ||
| Yacatisma | |||
| Yag-Kosha | Robert E. Howard's The Tower of the Elephant | Humanoid elephant | |
| Yaetuans | Christan Clines's The Yaetuan Sagas | Six limbed intelligent species | |
| Halo | |||
| Predator | Humanoid. Also known as Predators. They are a warrior race that hunts down other sentient races for sport, but follow a code of honor and deeply respect those who manage to defeat one of their own in combat. | ||
| Yariru | Vampire Idol | Vampire-humanoids | |
| Yazirian | Star Frontiers | Ape-like humanoid glider | |
| Yeerks | K. A. Applegate's Animorphs | Slug-like parasites. They need a host to see, walk, and communicate, and are the main antagonists of the Animorphs series, intent on enslaving other species. | |
| Star Control | Pterodactyl-like | ||
| Doctor Who | |||
| Sesame Street | |||
| Yliis | |||
| Jimmy Neutron | Gooey Slug-like aliens with egg shaped suits. | ||
| Yomingans | Schlock Mercenary | ||
| Yor | Galactic Civilizations | ||
| Yorn | Star Control 3 | ||
| Ythrian | Poul Anderson's Technic History | Eagle-like aliens | |
| Star Trek | |||
| Yugopotamians | The Fairly OddParents | Squid-like aliens with dome-covered brains. | |
| Star Wars | Humanoid |