鲻鱼，又称乌鱼，俗名青头仔（幼鱼）、奇目仔（成鱼）、信鱼、正乌、九棍、乌头，为辐鳍鱼纲鲻形目鲻科的其中一种。

本鱼体圆而长，头部略扁而尾部稍侧扁。成鱼之脂性眼睑发育完善，有时将瞳孔完全掩盖。主上颌骨不向下弯至前颌骨下方。背部中央无隆起棱脊。体侧有6至7条暗色纵带，胸鳍基部上半1/2处有一黑色斑块。具有巨大的背鳍上有硬棘4枚和软条8枚，臀鳍鳍条8枚。整个身体有栉鳞，并常有黏液分泌，以增加保护性。其身体虽无侧线。体长可长120公分。

The flathead grey mullet (Mugil cephalus) is an important food fish species in the mullet family Mugilidae. It is found in coastal tropical and subtropical waters worldwide. Its length is typically 30 to 75 centimetres (12 to 30 in). It is known with numerous English names, including the flathead mullet, striped mullet (US, American Fisheries Society name), black mullet, bully mullet, common mullet, grey mullet, sea mullet and mullet, among others.