The winter flouner, Pseudopleuronectes americanus, (also known as black back) is a flatfish of the family Pleuronectidae. It is native to coastal waters of the western north Atlantic coast, from Labrador, Canada to Georgia, United States. In the waters from Newfoundland down through Maryland it is the most common flounder. It grows up to 64 cm in length and 3.6 kg in weight.