Multiple realities(covers information from several alternate timelines)
Tranquility Base was a location on Luna, part of Mare Tranquillitatis ("the Sea of Tranquility"). In 1969, the area was the site of the first Human moon landing by Apollo 11's Lunar Module Eagle. (TOS: "Tomorrow is Yesterday")
By the 23rd century, a Starfleet shipyard was located there. Among the ships built there was the USS Defiant. (ENT: "In a Mirror, Darkly")
By 2364, a starship had been named for this location. (TNG: "Conspiracy", okudagram)
In the mirror universe, in the mid-2250s, the ISS Discovery was commissioned at this universe's equivalent of the base. The base was mentioned on the ship's dedication plaque. (DIS: "Despite Yourself")
According to the dedication plaque seen on the bridge of the
Defiant, this is where the ship was constructed, though this was never mentioned in dialogue.
In the Ships of the Line book, the
Defiant's sister ship, the USS Excalibur, was, according to a dedication plaque, commissioned at this base as well.