The Alpha Onias system was an uninhabited but strategically significant planetary system in the Beta Quadrant. This system, located within the Onias sector, was located near the Romulan Neutral Zone in the mid-24th century. The system's primary was named Alpha Onias.

In 2267, during the first Federation-Klingon War, this system was occupied by the Klingons. (DIS: "The War Without, The War Within")

In 2367, subspace anomalies were detected in this system, originating from Alpha Onias III. As there had been rumors about a secret Romulan base in the region for quite some time, the USS Enterprise-D proceeded to investigate it further. (TNG: "Future Imperfect"; DIS: "Magic to Make the Sanest Man Go Mad")

"OH-nye-is" was the pronunciation for this system's name from the script pronunciation guide.
Alpha Onias, the primary of the Alpha Onias system, was located in the Beta Quadrant on a star chart seen in the Star Trek: Discovery episode "Magic to Make the Sanest Man Go Mad".