The Gamma Hydra sector was a region of space which was located on the edge of the Coalition of Planets and bordered the Romulan Star Empire as well as the Klingon Empire. The sector is named for the prominent star system present, Gamma Hydra.

By the mid 22nd century, the sector was a source of constant skirmishes between the Romulans and Klingons. The Romulans were known to have placed gravitic mines in the region in order to dissuade the Klingons from claiming the region. In 2155, the freighter ECS Kobayashi Maru was struck by a gravitic mine and was eventually destroyed by three Klingon battlecruisers that were remotely controlled by Romulan forces. (ENT novel: Kobayashi Maru)

By the late 23rd century the sector was located at the very edge of Federation territory and shared a border with the Romulan Neutral Zone and the Klingon Neutral Zone. (TOS movie: The Wrath of Khan)