Tellar Prime, or Tellar, was an inhabited M-class planet and homeworld of the Tellarites, a warp capable humanoid species.
In 2155, Tellar became one of the founding members of the Coalition of Planets and later, in 2161, the United Federation of Planets. (ENT: "Demons", "Zero Hour")
Relative to the planetoid Babel, Tellar was located on the far side of the Andorian Empire. (ENT: "Babel One")
Good arguments were considered a sport on Tellar. (ENT: "Bounty")
Following the fall of Betazed during the Dominion War, in 2374, many believed that Tellar could be the Dominion's next target. (DS9: "In the Pale Moonlight")
The Tellar system was located in or near Federation space, in the Tellar sector (Sector 007), in the Alpha Quadrant. This binary star system, also known by its Bayer designation as 61 Cygni, had at least one planet. Tellar A was a K class star with a magnitude of +5, which was the same brightness as Sol. Tellar B was a K class star.
In the mid-22nd century, Tellar Prime was a destination on the Earth-Tellar run. In 2378, Tellar Prime was a Federation member. (pgs. 19, 36, 44, "United Federation of Planets I")