The USS Reliant (NCC-1864) was a 23rd century Federation Miranda-class starship operated by Starfleet. In 2285, the Reliant was commanded by Captain Terrell. While under his command, the ship's prefix code was 16309.
In 2285, the Reliant served at the disposal of Dr.s Carol and David Marcus during their research for Project Genesis. While Marcus and her team worked from the Regula I space station, Reliant searched for a lifeless planet to serve as a suitable test site to satisfy the stringent requirements necessary for stage three of the Genesis Experiment.
Ceti Alpha VI and Khan's revenge
On Stardate 8130, the Reliant approached the planet Ceti Alpha VI. During the scan of the planet, one of the Reliant's dynoscanners detected a "minor energy flux" on the surface on what seemed to otherwise be a prime location for the experiment. Hurried by the growing impatience their unsuccessful mission bore upon them, Captain Terrell and his first officer Pavel Chekov transported to the surface to investigate the energy flux, hoping that it was something they could "transplant" in advance of testing.
The landing party, however, instead discovered a group of exiles, led by Khan Noonien Singh. Khan and his followers quickly captured the two Starfleet officers and informed them that the planet Reliant was orbiting was not Ceti Alpha VI but actually Ceti Alpha V. Khan then took control of Terrell and Chekov through the use of Ceti eels and successfully hijacked the Reliant, marooning her crew on the planet's surface. Having learned of the Genesis Device, Khan pursued acquiring the secrets of the device that the Reliant was contracted to work for and took the Reliant to the Regula I space station.
The encounter between the Reliant and the Enterprise was witnessed by the Tardigrade "Ephraim" as she pursued the Enterprise, on which she had laid her eggs, many years previous. (ST: "Ephraim and Dot")
In an ambush, the Reliant caused severe damage to the engineering section of the Enterprise, but Khan was unable to revel in his victory because the Reliant itself fell victim to a counter-ambush from the Enterprise after its crew managed to partially disable its defenses by accessing them through the Reliant's prefix code.
The attack caused moderate damage to the Reliant, including the loss of photon torpedo control and the ship's warp drive. Despite the damage the Reliant escaped, and returned to Regula where it hid behind the planetoid while making repairs and awaiting the next opportunity to engage Enterprise. Khan took up the pursuit shortly afterwards when hailed and taunted by Kirk into the Mutara Nebula.
The final engagement
- See main article: Battle of the Mutara Nebula
After completing repairs, Khan discovered that the Enterprise was not as crippled as he was led to believe and gave chase when he discovered the Enterprise making a run for the nearby Mutara Nebula. Despite having the tactical advantage over the Enterprise, Khan ultimately lost the battle due to his lack of strategic experience operating a starship. The Enterprise was able to take advantage of this weakness by outmaneuvering the Reliant and critically disabling it with phaser bursts and photo torpedoes, destroying much of its upper weapons pylon and finally its port nacelle.
The Reliant was ultimately destroyed inside the nebula by Khan's detonation of the Genesis Device. The crew was rescued from Ceti Alpha V shortly afterward by the Enterprise. (Star Trek II: The Wrath of Khan)
USS Reliant personnel
The Reliant was originally intended to be a Constitution-class starship; the script describes her as "an older, somewhat battered starship of the Enterprise class, with a slightly different configuration."  The cumbersomeness of the Enterprise studio model from Star Trek: The Motion Picture (vehemently expressed by Special Visual Effects Supervisor Kenneth Ralston at the time) was part of the reason why the class of the Reliant was redesigned from a Constitution-class to the Miranda-class, the other reason being that the producers were afraid that audiences would not be able to tell the two ships apart during the battle sequences. "In the dogfight you had to instantly recognize which ship you were looking at, so they had to look different. At the same time, you had to make them look like they came from the same culture and had the same technology", Joe Jennings elaborated. (Star Trek: The Magazine Volume 3, Issue 5, p. 69)
Her name meaning "dependent", the Reliant was designed by Joe Jennings and Mike Minor and was the first distinct Federation starship design other than the NCC-1701 to appear in a filmed, live-action Star Trek production.
The Reliant bridge was simply a redress of the bridge of the Enterprise.
One of the Miranda-class starships seen in the Star Trek: Deep Space Nine episode "Tears of the Prophets" bore the registry number NCC-1864. The ship in question was one of the two ships described by David Stipes as being either the USS Nautilus (NCC-31910) or USS Tian An Men (NCC-21382). 
In the 2012 Star Trek: Ships of the Line calendar, for the month of July, the Reliant appeared in an alternate timeline approaching a Spacedock-type space station named Spacedock Tango Sierra (β). In the 2015 Star Trek: Ships of the Line, for the month of August, Reliant appeared opposite the Enterprise-A, in a spread titled 'Joint Operations'. In the 2018 Star Trek: Ships of the Line, for the month of May, Reliant appeared again, this time being depicted as undergoing repairs with the Enterprise nearby.
According to the Lost Era novel The Sundered, the Reliant visited the Halkan homeworld in 2281 to respond to an attack by Orion pirates. While leading an away team on the surface, Pavel Chekov met a young Halkan named Lojur, who had been exiled by his village elders for using deadly force against the attackers, which violated the Halkans' strict pacifism. Chekov took the young exile with him back to the Reliant; Lojur later joined Starfleet and served on board the USS Excelsior.
Both the novels Star Trek: The Wrath of Khan and the To Reign in Hell: The Exile of Khan Noonien Singh indicate that in addition to Captain Terrell and Commander Chekov, Khan also used Ceti eels to take control of the ship's engineering crew. To Reign in Hell also states that Khan killed or maimed several members of Reliant's crew in a fit of pent-up rage (described as "a vicious prelude to the massacre at Regula I"), with ten dead before they were rescued.