The so-iuy mullet (Planiliza haematocheilus), also known as the haarder, redlip mullet or so-iny mullet, is a species of ray-finned fish in the family Mugilidae.

[2] Previously the species was included in the genus Mugil (as Mugil soiuy), but is now considered a member of the genus Planiliza.

[3][4] The natural range of the species is in the Northwest Pacific, from Hokkaido and the Amur River in the north along the coasts of Korea and China to Vietnam in the south.

[7] There are 69 known species of parasites of Planiliza haematocheilus.

This Mugiliformes-related article is a stub.