The Cytherians are an advanced sapient species inhabiting the deep core region of the Milky Way galaxy. They typically manifest themselves in the form of a translucent humanoid head; and are probably non-corporeal entities.
Cytherians identify themselves as explorers, willing to know about other species, however their methods are most unorthodox. Rather than exploring the galaxy by themselves, they send automatic probes which are capable of altering the nervous system of other lifeforms that make contact with them, temporarily granting them with extraordinary mental abilities and a strong desire to create the technology necessary to reach the galactic core. Hence, the Cytherians bring other civilizations to themselves, benefiting their new acquaintances in the process.
- Although not confirmed by official sources, it is widely believed that the powerful entity encountered at the galactic center in the movie Star Trek V: The Final Frontier was a rogue Cytherian; possibly imprisoned or exiled by his people.
- The word "Cytherean" has been used as a synonym for Venusian. In the context of the Star Trek universe, this is probably just a coincidence, though.