Tanis was a planet located in Federation space, somewhere in the galaxy's Alpha or Beta Quadrants.
History and specifics[]
Tanis had little atmosphere and no native lifeforms.
In the year 2268, Tanis Base, a secret Federation outpost, was established on Tanis. In 2270, the USS Enterprise visited Tanis in response to a distress call sent by Dr. Jeffrey Adams. (TOS novel: Bloodthirst)