A Starfleet vessel named in 2364 as the final starship command of Admiral Mark Jameson, the negotiator whose secret arms deal on Mordan IV led to decades of civil war.
The USS Gettysburg is mentioned in the first-season Next Generation episode Too Short a Season. When Admiral Mark Jameson comes aboard the Enterprise-D to deal with a hostage crisis on Mordan IV, his service record is discussed, and the Gettysburg is given as the last ship he commanded before taking a desk post.
The ship itself is never seen and plays no part in the events on Mordan IV, where Jameson's earlier decision to arm both sides of a dispute is finally exposed by Governor Karnas.
Its name follows the Starfleet habit of honouring historic battles and places. Reference works have described it as a Constellation-class vessel, but nothing in the episode confirms the class or a registry number.