The USS Yamaguchi (NCC-26510) was a Federation Template:ShipClass heavy cruiser that was in service with Starfleet in the mid-24th century.
In 2367, the Yamaguchi participated in the battle against the Borg at Wolf 359 in the fleet of forty Federation starships. She engaged the attacking Borg cube, alongside the USS Bellerophon, at the time the cube had tractored the USS Saratoga. She was presumably one of the 39 ships destroyed in the battle. (DS9: "Emissary")
Yamaguchi literally means "mountain mouth" in Japanese. The name was also a prefecture in Japan, as well as a common Japanese surname.