L-374 IV

From Memory Alpha, the free Star Trek reference.

The M-class world L-374 IV was the fourth planet in the L-374 system.

In 2267, Science Officer Masada of the USS Constellation picked up scans that the planet was being broken up by what was later known as the "Doomsday machine". The captain of the Constellation, Commodore Matt Decker, ordered his crew to attack and destroy the machine. Despite their efforts, the doomsday machine destroyed the entire planet. All the inhabitants of the planet were killed. (TOS: "The Doomsday Machine")