The USS Constellation (NCC-1974) was a Constellation-class starship in service in both the 23rd and 24th centuries, and the prototype for the Constellation-class.
In 2293, the Constellation still held an NX registry number as it completed certification trials. (Star Trek VI: The Undiscovered Country)
Fresh from the Academy, Dr. James Maxwell joined the Constellation medical team as assistant chief medical officer in 2344. Dr. Jason Hargreaves was his superior. (Star Trek: New Frontiers)
The Constellation arrived at Deep Space 9 in 2371 to ferry a Jem'Hadar child to Starfleet for study. (DS9: "The Abandoned")
In 2374, the ship assisted the USS Defiant, searching for survivors from the USS Honshu, which was attacked by the Cardassians during the Dominion War. (DS9: "Waltz")