The Immortal appear to be a sub-species of Human that are very difficult, if not impossible, to kill. Immortals are very similar to Humans, yet cease ageing at a point, and can heal from all injuries almost instantaneously.
- Flint - currently believed to be dying, but was still alive in 2374.
- Morgan Primus - was killed by the Beings and transferred her consciousness to the USS Excalibur computer system.
- Tarella Lee - killed herself with Promethean weaponry.
- Malok - Left alive by Spock on Pollux II, but inhabited by Vulcan emotions.
- TOS short story: "The Immortality Blues"
- TOS novel: Federation
- TOS episode: "Requiem for Methuselah"
- TOS novel: The Cry of the Onlies
- TOS novel: The Rise and Fall of Khan Noonien Singh, Volume 1
- NF novel: Fire on High
- NF novel: Renaissance
- NF short story: "Lefler's Logs"
- NF short story: "Alice, on the Edge of Night"
- TNG short story: "The Other Side"
- TNG novel: Immortal Coil
- NF novel: Being Human
- NF novel: Gods Above
- NF novel: Missing in Action
- NF comic: "Turnaround, Part I"
- TNG novel: Greater Than the Sum
- Star Trek: Myriad Universes novel: Seeds of Dissent