Outpost 61 was a Cardassian outpost located in the Almatha sector along the border with the Federation that served as both defense and advanced warning. On Stardate 48467.3, it was under the command of Gul Toran of the Sixth Order.
Outpost 61 came under attack by a Maquis ship that disguised its warp signature so it would be mistaken for the USS Defiant. Its purpose was to draw away Cardassian ships so that the real Defiant could then attack their true target, Outpost 47.
The Defiant had been stolen by a Maquis operative, Lieutenant Thomas Riker. (DS9: "Defiant")
According to the Star Trek: Star Charts, on page 47, Outpost 61 was located in the Alpha Quadrant.