全头亚纲（学名：Holocephali）是软骨鱼纲下的亚纲，颌全接型，舌弓完全，无鳞，胸鳍宽大，尾鳍细长，雄性具交接器。

现存全头亚纲只有一目：

• 银鲛目（Chimaeriformes）

The subclass Holocephali ("complete heads") is a taxon of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. Little is known about these primitive forms, and the only surviving group in the subclass is the order Chimaeriformes. This group includes the rat fishes in the genus Chimaera, and the elephant fishes in the genus Callorhynchus. These fishes move by using sweeping movements of their large pectoral fins. They have long slender tails and live close to the seabed feeding on benthic invertebrates. They lack a stomach, food moving directly into the intestine.