The USS Defiant (NX-74205) was a 24th century Federation Defiant-class starship operated by Starfleet and the Alliance. This was the prototype of the class and the second Federation ship known to bear the name Defiant. Development on the Defiant began around the first war in response to the Borg threat. Although officially classified as an escort vessel, the Defiant was nothing less than Starfleet's first design of warship; intended to fight, and ultimately defeat, the Axis. The vessel featured minimal equipment for scientific research and was not designed to accommodate families.
The class was originally developed to counter the Borg, however the Defiant was assigned to starbase Deep Space 9 in light of the increasing threat of the Dominion joining the Coalition. In exchange for intelligence data on the Dominion, the Defiant was equipped with a cloaking device on loan from the Romulan Star Empire. Benjamin Sisko was involved in the development of the Defiant, and served as the ship's commanding officer throughout her service. The Defiant was a participant and flagship throughout the Dominion War, until her destruction by the Imperialists at the Second Battle of Chin'toka in the Second War. Her successor was the USS São Paulo, which was re-named and registered to the Defiant's name and registration in honor of the fallen vessel.