Epsilon Outpost 15 was a Federation Epsilon Outpost operated by Starfleet. This outpost was located near the Romulan Neutral Zone.
In 2259, the location of this outpost was labeled on a stellar cartography chart that was seen on the USS Enterprise's ready room viewscreen. (SNW: "A Quality of Mercy")
In the early 24th century, the location of this outpost was labeled in a chart used during a Section 31 Alpha Team briefing. (Star Trek: Section 31)
This outpost was only mentioned in writing.