Theta VII colony
The Theta VII colony was a Federation colony on the planet Theta VII. The colony was located somewhere in the Alpha or Beta Quadrant.
In 2268, a disease caused a medical emergency here and vaccines were desperately needed. The USS Yorktown transported these vaccines and transferred them to the USS Enterprise, which then delivered them to the colony. (TOS: "Obsession")
Appendix
Background Information
This colony was only mentioned in dialogue.
In the Star Trek: Star Charts ("United Federation of Planets I"), Theta VII was a Federation member in 2378.
Apocrypha
In the Star Trek Maps (p. 30), the Theta VII colony, established in 2147, was located on the only M class planet of the eleven planets that orbited the blue giant star Theta. The mining and farming colony was built underground to shield the inhabitants from solar flares. The colony had a population of 14,500.