有颔下门（Gnathostomata）原为有颔总纲（Gnatha），是脊椎动物亚门中拥有颔的一群，与无颔总纲相对应，属于较高等的一类。此总纲下分成数个纲：

有颔下门生物之下颌骨系于距今约四亿三千万年前开始发展形成，即无颔总纲生物面世约一亿年后。

Gnathostomata /ˌneɪθoʊstoʊˈmɑːtə/ are the jawed vertebrates. The term derives from Greek: γνάθος (gnathos) "jaw" + στόμα (stoma) "mouth". Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates. In addition to opposing jaws, living gnathostomes also have teeth, paired appendages, and a horizontal semicircular canal of the inner ear, along with physiological and cellular anatomical characters such as the myelin sheathes of neurons. Another is an adaptive immune system that uses V(D)J recombination to create antigen recognition sites, rather than using genetic recombination in the variable lymphocyte receptor gene.