Ilidaria was an inhabited planet in the Ilidaria system in the Delta Quadrant. This planet was located less than three light years from a type-4 quantum singularity. Its inhabitants had sophisticated technology and were "quite friendly, most of time". (VOY: "Parallax")
According to the
Star Trek Encyclopedia (3rd ed., p 204), this was the homeworld of the Ilidarians to which a trade mission was conducted later that season.