The Guardian class was a type of escort that served in the Federation Starfleet during the 23rd century.
The class entered service in 2229. By 2258, Starfleet decided that the class was no longer worth upgrading and started to design a replacement. A decade later, the Hellespont-class entered service to replace the Guardian and Majestic-class escorts. (Ship Recognition Manual, Volume 4: Starships of the Original Series Era)