鳗鱼是指属于鳗鲡目分类下的物种总称。是一种外观类似长条蛇形的鱼类，具有鱼的基本特征。此外鳗鱼与鲑鱼类似具有洄游特性。

鳗鲡目下分3个亚目，如下：

• 鳗鲡亚目(Anguilloidei)
• 鯙亚目(Muraenoidei)
• 糯鳗亚目(Congroidei)

An eel is any fish belonging to the order Anguilliformes (/æŋˌɡwɪlᵻˈfɔːrmiːz/), which consists of four suborders, 20 families, 111 genera and about 800 species. Most eels are predators. The term "eel" (originally referring to the European eel) is also used for some other similarly shaped fish, such as electric eels and spiny eels, but these are not members of the Anguilliformes order.