A strip of space separating the United Federation of Planets from the Klingon Empire during the 23rd century, which neither side's warships were meant to enter without provoking an incident.
The Klingon Neutral Zone is the buffer between Federation and Klingon territory in the era of Kirk's Enterprise, a product of the uneasy peace that followed the events of Errand of Mercy.
It is best known from the Kobayashi Maru scenario that opens The Wrath of Khan, in which a cadet must decide whether to enter the zone to rescue a crippled freighter and face Klingon cruisers. Disputes over worlds near the border also drive episodes such as The Trouble with Tribbles.
In The Undiscovered Country, the destruction of Praxis in 2293 leads Chancellor Gorkon to propose peace, and the Khitomer conference sets in motion the dismantling of the zone and of the outposts along it.