The Onias Sector is a section of space inside Federation territory, but near the often contested tri-border between the Federation, Klingon Empire, and Romulan Star Empire.

Sometime prior to 2156, the Federation started mining operations in the sector. In 2156, a fleet of Romulan warships attacked the NX Columbia while it was escorting a convoy of mining vessels. The Romulans were able to plant a Trojan virus into the Columbia's computer systems, took control of the ship, and used it to destroy the convoy. The Columbia was able to later escape by detonating a photonic torpedo and making a warp jump to make it look as though the ship self-destructed.

In 2381, the USS Amargosa was defending the Onias Sector along with four other starships when the fleet was attacked and destroyed by the Borg. (ST - Destiny novel: Gods of Night)