Triannons are a fictional race from the Star Trek universe who appeared in the Star Trek: Enterprise episode "Chosen Realm". Their homeworld is called Triannon and is located in the Delphic Expanse.

Triannons are very religious. They call the Expanse the "Chosen Realm" and view the Expanse's mysterious spheres as religious shrines. They also believe that the spheres were created by divine beings called "Makers" who would one day return. The spheres, they believe, were being used to reshape the Expanse into a paradise for themselves.

Those who believe in this sacred truth are willing to kill all those who do not. For over 100 years, a war was fought on Triannon simply because the Heretics believed that the Expanse was created in ten days as opposed to the Triannons' belief in the sacred truth that stated it took only nine days.

In 2153, a group of Triannons encountered the Earth ship Enterprise NX-01. They hijacked the ship and attempted to use it in a final attack against the Heretics. When they fought a fleet of Heretic ships, the crew of Enterprise was able to regain control the vessel and halted the attack.

When Enterprise arrived at Triannon, Capt. Archer showed the Triannons that religious war had devastated the planet by killing millions of inhabitants and had destroyed all the major cities.