The Magellanic Flightless Steamer Duck, Tachyeres pteneres, is a flightless duck from South America. It belongs to the steamer duck genus Tachyeres. It is a massively built "duck" at 3.5-7 kg (7.7-15.5 lbs) and 65-78 cm (22-31 in), with the males larger than the females.

This species is locally infamous for the aggressive disposition of adult males. Incidents have allegedly occurred where a raging male was placed by a misguided collector among adults of various other waterfowl species and killed all the other birds with their powerful, spurred wings.