Tau Ceti was a system centered around a star located about 11.8 light years from Sol. This location is mentioned in communications that are part of Starfleet Academy's Kobayashi Maru scenario. (Star Trek II: The Wrath of Khan)
At some point prior to 2268, the USS Enterprise, under the command of Captain James T. Kirk, engaged and defeated a Romulan vessel near Tau Ceti, using the Cochrane deceleration maneuver. (TOS: "Whom Gods Destroy")
This system was the site of the Tau Ceti Accords signed between the Vulcan High Command and the Andorian Empire. (ENT: "Shadows of P'Jem")
Tau Ceti is notable in the mirror universe, as the system in which the Terran Empire lost twelve ships in a battle against alien rebels. Propaganda had spread that this was a major win for the Terran Empire, when in fact it was a sign they were beginning to lose. (ENT: "In a Mirror, Darkly")
In 2364, Tau Ceti was noted on a large star chart at Starfleet Headquarters. Also, on several other occasions that year, viewscreen readouts aboard the USS Enterprise-D showed the location of Tau Ceti, in the form of charts from the Enterprise library computer. (TNG: "The Naked Now", "The Last Outpost", "Conspiracy")
Tau Ceti I
Tau Ceti I is a class Y planet. It is extremely inhospitable.
Tau Ceti II
Tau Ceti II is the home of an expatriot Native American Indian tribe. They fled Earth in disgust just after Zephram Cochrane invented warp drive.
Tau Ceti III
Tau Ceti III is the third planet in the Tau Ceti system. Jean-Luc Picard first met Walker Keel at "quite an exotic" bar on Tau Ceti III. (TNG: "Conspiracy")
- According to a non-canon source, The Worlds of the Federation, Tau Ceti III is the origin of Kaferian apples, and the Kaferian insectoids who live on Tau Ceti III refer to this world as Kohath-Seredi.
Tau Ceti IV
Tau Ceti IV is the fourth planet in the Tau Ceti system.
During the 23rd century, the Tau Ceti city of Amber was the homeport of the 3rd class neutronic fuel carrier Kobayashi Maru, and her master Kojiro Vance. (Star Trek II: The Wrath of Khan)
- This information was found on the Kobayashi Maru scenario data screen. It is unknown whether this information is factual or fictional.
Tau Ceti Prime
Tau Ceti Prime is a planet in the Tau Ceti system. Vice Admiral Janeway died on Tau Ceti Prime, drowned under an ice cap. (VOY: "Coda")