The USS Guardian was a Capella class escort serving in Starfleet during the 24th century.
Emerson Ames served aboard the ship in the 2360s. During that time she was part of the First Fleet under Commander Alvaro Tejedor. ("Aiding & Abetting")
After the call went out for all available ships to assemble at Wolf 359, the escort joined eleven ship flotilla that arrived seventeen hours later.
In late 2371 the escort was part of the task force to free the Psellus System from Romulan forces. ("Armistice Part II")