Patagonotothen ramsayi, the longtail southern cod, is a benthopelagic species of marine ray-finned fish of the family Nototheniidae, the notothens or the cod icefishes, native to the Patagonian Shelf in the southwest Atlantic, where it is the most abundant notothen species found, dominating among medium-sized demersal fishes in the area, and is a commercially important species.