The olive flounder, bastard halibut or Japanese halibut, is a temperate marine species of large-tooth flounder native to the North-western Pacific Ocean.
It is often referred to as the Japanese flatfish or Korean flatfish (광어) when mentioned in the context of those countries. It is the highest valued finfish in the world, known to be excellent for aquaculture due to a rapid growth rate and popularity in Korea.
It reaches a length of 103 cm (41 in) and a weight of 9.1 kg (20 lb). In 2017 its genome and transcriptome was sequenced as a model to study flatfish asymmetry.