The advanced, peaceful outer planet of the M43 Alpha system, threatened with invasion by the Nazi-style regime of Ekos.
Zeon is the outer inhabited planet of the M43 Alpha system and home to the Zeons, a peaceful, technologically advanced people. Some Zeons have settled on neighbouring Ekos, where the regime built by John Gill and Melakon blames them for the planet's troubles.
In Patterns of Force, Melakon is preparing a fleet to destroy Zeon. Kirk and Spock, working with Zeon and Ekosian resistance members, stop the invasion when Gill publicly orders it called off.