The USS Gettysburg was a 24th century Federation starship operated by Starfleet. This starship was the last command of Mark Jameson and the last location of space travel for him before 2364. (TNG: "Too Short a Season")
This starship was only mentioned in dialogue.
In an internal list of starships, from 26 September 1990, the Gettysburg's (spelled in the list as Gettysberg) registry number was NCC-38902. 
In a scene cut from the final episode, the other ships that Jameson was the commanding officer of were named the USS Falcon and the USS Pegasus. According to this scene, by 2364, the Gettysburg was renowned for its explorations.