List of unnamed stars.
Alpha and Beta Quadrants
Argolis Cluster star
Borg renegade star
Deinonychus system star
Dyson sphere star
In 2368 during the Klingon Civil War, Kurn used a clever technique of engaging warp drive near this star's surface, causing a solar flare which destroyed the two Klingon pursuers. (TNG: "Redemption II")
Kuiper belt star
Sector 396 Star
Supernova of 2387
In 2387, a star in close proximity to Romulus went supernova and threatened the galaxy. To stop the threat, Ambassador Spock used red matter to create a black hole which consumed the star's energy. Before he could successfully carry out his mission, however, the supernova reached Romulus, destroying the planet and all of its inhabitants. Among those killed were the wife and unborn child of Nero, who swore vengeance against Spock, Vulcan, and the Federation for letting his world die. While Nero confronted Spock, both of their ships were pulled into the black hole which had consumed the star, sending them back in time and resulting in the creation of the alternate reality. (Star Trek)
Having a supernova threaten the entire galaxy is a physical impossibility under normal circumstances due to the laws of physics limiting its expansion rate to below the speed of light, and the expansion of the blast wave would result in it dissipating after traveling perhaps a few dozen light-years.
In the comic book series Star Trek: Countdown, this star and its system were named "Hobus". The comic explained that the star's galactic threat came from its unusual ability to transform anything it contacted into energy, which it then consumed, increasing its power and causing it to expand farther and faster throughout the galaxy.
The Star Trek novelization instead stated that the star had merely threatened systems in its own vicinity rather than the entire galaxy.
A third explanation appears in the backstory of Star Trek Online, which states that the shockwave propagated through subspace at faster-than-light speeds. Also in the game's backstory, a scandal occurred several years later involving rumors that the Vulcan Science Academy knew about the instability of the star but did nothing until Spock attempted to save Romulus with the Jellyfish. The scandal resulted in several resignations and sowed seeds of distrust towards the Vulcans.
It is also confirmed by the Featured Episode series "Cloaked Intentions" that Remus was also destroyed, however the Romulans and Remans still continue their prejudices towards each other. It is also revealed that the supernova was not a natural occurrence, but was engineered by then-Praetor Taris, who did so under orders from the Iconians.
Sector 1156 star
Tamaal's system stars
Alastria twin suns
Class D planet star
Star near rogue comet
Star in Swarm species space
Supernova of 2373 (natural)
Supernova of 2373 (caused by Q)
J class gas giant star
A J class gas giant in the Gamma Quadrant was orbiting this sun. In 2372, the USS Defiant entered the atmosphere of the class J planet to rescue the crew of a Karemma ship. The Karemma were attempting to escape from two Jem'Hadar ships.(DS9: "Starship Down")