缩头水虱科（Cymothoidae）是等足目之下的一个科，包含多种寄生生物，通常寄生在鱼类的身上，例如：缩头鱼虱。现时本科之下总共有40个可辨别的属，分别如下：

The Cymothoidae are a family of isopods in the suborder Cymothoida and are found in both marine and freshwater environments. Cymoithoids are ectoparasites, usually of fish, and among their number they include the bizarre "tongue-biter" (Cymothoa exigua) which attaches to a fish's tongue causing it to atrophy, and replaces the tongue with its own body. Around 40 genera and more than 380 species of cymothoid are recognised.