NGC 321
NGC 321 is a star cluster. This cluster contains the Eminiar system, which is home to the planets Eminiar VII and Vendikar.
In 2267, the Federation dispatched Ambassador Robert Fox aboard the USS Enterprise to negotiate a treaty port there. Federation authorities were concerned over the large number of deaths in the sector, and sought the treaty port to lessen the hazards. Fox ultimately remained on Eminiar to help negotiate a peace treaty that ended the Eminians' five-century war with Vendikar. (TOS: "A Taste of Armageddon")
Background
In the New General Catalogue, NGC 321 was a distant galaxy without any known stellar components inside our galaxy, however later Star Trek episodes show us that Eminiar couldn't have been traveled to if it was distant by intergalactic means.