Tau Ceti is the most Sun-like of the 30 nearest stars to the Sun. It lies in the constellation Cetus and is easily visible without a telescope. Tau Ceti has been the target of many SETI (Search for Extraterrestrial Intelligence) programs including the first, Project Ozma, which also looked at Epsilon Eridani. It is also the first star to be found to have a disk of dust and comets around it similar in size and shape to the disk of comets and asteroids that orbits the Sun. However, the similarity ends there because it appears that Tau Ceti has more than ten times the number of comets and asteroids that there are in our Solar System.

In Star Trek, 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").

Vice Admiral Janeway (the father of Captain Kathryn Janeway of the USS Voyager) died on Tau Ceti Prime, drowned under an ice cap. (VOY: "Coda")

In reality, Tau Ceti is a main sequence, yellow-orange dwarf (G8 Vp) that may be as much as 10 billion years old. It has about 81 to 82 percent of Sol's mass, around 77 percent its diameter, but only 59 percent of its luminosity (Saumon et al, 1996, page 17). The star does not appear to be as enriched as Sol in elements heavier than hydrogen ("metals") because it has only 22 to 74 percent of Sol's abundance of iron.

It is not known if the star is accompanied by any planets – its low metallicity makes it questionable whether the nebula from which it condensed had sufficient heavy element content to allow planet-sized objects to form). However, if any planets are present, as hypothesized in the accompanying painting, they are likely to be subjected to a much more intense bombardment than anything the Earth has experienced, making the survival of any life problematic.

This star is located only about 11.9 light-years (ly) away. It lies in the south central part of Constellation Cetus, the Whale. While smaller and cooler than our own Sun, Sol, Tau Ceti is somewhat more like a sister star than nearby Epsilon Eridani. In Earth's night sky, it is clearly visible to the naked eye and easily visible without a telescope.

In July 2004, astronomers announced that they had imaged a relatively large and dense disk of cold dust around this star. Tau Ceti has more than ten times the amount of cometary and asteroidal material orbiting it than does our Sun. This was determined by measuring the disc of cold dust orbiting the star produced by collisions between such small bodies. Extending to around 55 AUs from the star, this dust is believed to be produced by collisions between larger comets and asteroids that break them down into smaller and smaller pieces, and Tau Ceti's disk is similar in size and shape to the disk of comets and asteroids that orbits the Sun, Sol. Given Tau Ceti's estimated age of 10 billion years, the estimated mass of its dust disk fits its expected decline with time compared to the disk mass of the younger nearby star Epsilon Eridani, which may only be 500 million to one billion years old. This result puts a damper on the possibility of complex life in this system, as planets there would suffer from large impact events roughly ten times more frequently than Earth. However, it is possible that a large Jupiter-sized gas giant could deflect comets and asteroids

Why the Tau Ceti System would have a more massive cometary disk than the Solar System is not fully understood. One theory is that Sol may have passed relatively close to another star at some point in its history and that the close encounter stripped off most of its comets and asteroids. Although no planets have been detected orbiting Tau Ceti as yet, it is likely that any planet found to orbit within the star's dust disk would experience relatively frequent bombardment from asteroids and comets of the size that is believed to have wiped out the dinosaurs and other types of multi-cellular life on Earth. As a result, some astronomers have speculated that it is likely that with so many large impacts, large and complex forms of Earth-type multi-cellular life may not have had the opportunity to evolve and persist on inner terrestrial planets orbiting this star. Others, however, argue that a giant planet in the system could gravitationally deflect comets and asteroids away from inner planets that may support life in the liquid water zone, in the same way that Jupiter protects Earth in the Solar System.