T'lli Beta was an inhabited planet in the T'lli Beta planetary system. This was the homeworld of the T'lli Betans.

In 2367, the USS Enterprise-D was en route to T'lli Beta before it was ensnared by the gravitational pull of a cosmic string fragment which a group of two-dimensional lifeforms were attempting to enter. (TNG: "The Loss")

T'lli Beta also appeared in the starchart Data and Picard were studying in stellar cartography in 2371. (Star Trek Generations, display graphic)