囊鳃鳗目是一种条鳍鱼（辐鳍鱼纲），在一定程度上与真鳗较为相似，但是有很多内部结构上的差异。从已有的少量标本来看，大部分的囊鳃鳗目都是深海鱼类，比如伞口吞噬鳗。

囊鳃鳗目缺少部分骨骼，如续骨、鳃盖骨及肋骨。他们也没有鱼鳞，腹鳍或鱼鳔。口部一般较大，其中部分甚至可以吞噬下比自身更大的鱼类而令人印象深刻。它们的myomeres(肌肉 segments)呈V字体而不是其他鱼类的W字体，并且它们的侧线不具备开孔，而是由一组管道代替。

Saccopharyngiformes is an order of unusual ray-finned fish, superficially similar to eels, but with multiple internal differences. Most of the fish in this order are deep-sea types known from only a handful of specimens, such as the pelican eel. Some species are bioluminescent. Some, such as the "swallowers", can live as deep as 3,000 m (10,000 feet) in the ocean, well into the aphotic zone. Saccopharyngiformes were found by deep sea fishermen's nets. Extensive research has not been conducted on them due to being indirectly observed.