The Gav'Nor was a 31st century starship destroyed by the Burn circa 3069.
In 3189, Michael Burnham obtained the black box of the Gav'Nor for her research into the Burn; its data was displayed with other evidence on a holographic note board in her quarters aboard the USS Discovery. It was determined that the destruction of the Gav'Nor occurred one one-millionth of a millisecond after the USS Yelchin, located a thousand light years away, indicating that the event was not simultaneous. (DIS: "Forget Me Not", "Unification III")
Mario Moreira noted in TRR: "There Is A Tide..." that the Gav'Nor was a Cardassian ship, operated while the Cardassians were members of the United Federation of Planets.