L-374 III was the third planet in the L-374 planetary system. This was one of two planets destroyed in the planet killer attack of 2267; the other was L-374 IV. The other two planets in the system, L-374 I and L-374 II, were spared.
In 2267, the entire crew of the Federation starship USS Constellation, consisting of 400 men and women, was beamed down to this planet for safety against the planet killer which was attacking the Constellation with her Captain, Commodore Matt Decker still aboard the starship trying to outrun the machine. When the Constellation was disabled, the Doomsday machine turned onto L-374 III. Severely damaged and with transporters offline, there was nothing Decker could do to save his helpless crew.