The Arritheans were a warp-capable species from the Delta Quadrant.
In early 2374, the race was encountered by the USS Voyager. Neelix carried out the early negotiations in his capacity as ship's ambassador. A trade meeting later took place. (VOY: "Revulsion")
This species was only mentioned in dialogue.
According to Star Trek: Star Charts (p. 88), there was a star system named Arrithea, which might possibly be the system of origin for this species, in the quadrant. The primary of this system was a K-class star. The Voyager visited this system on stardate 51188.