A Delta Quadrant species in conflict with the Taresians, whose ships attack those the Taresians lure to their world, as Voyager learned when Harry Kim fired on them in 2373.
The Nasari are a spacefaring humanoid species who appear in the Voyager episode Favorite Son. Voyager first meets a Nasari vessel in apparently peaceful circumstances, but Harry Kim, gripped by an unaccountable conviction that it is about to attack, opens fire on it without orders.
Sensor logs bear him out, since the Nasari had been charging weapons. Kim's strange knowledge leads the ship to Taresia, whose people claim him as one of their own. More Nasari ships gather and blockade the planet.
The truth is that the Taresians had infected Kim with a retrovirus to draw him to them, as they need males from other species in order to reproduce, at the cost of the men's lives. The Nasari captain, Alben, knows the danger well. Voyager snatches Kim away and leaves the two sides fighting.