Eucteniza ( /juːktəˈnaɪzə/ yook-tə-NY-zə[1]) is a genus of trapdoor spiders in the family Euctenizidae containing at least 14 species occurring in Mexico and the southern United States.

Species are distinguished by a softened rear portion of the carapace, and males possess large spines on the first two pairs of walking legs that are used to hold females during mating.

Like other trapdoor spiders they create burrows with a hinged lid, from which they await passing insects and other arthropods to prey upon.

The cephalothorax (the anterior body segment bearing the eyes, mouthparts, and legs) is oval, slightly longer than wide, and slopes considerably towards the rear when viewed from the side.

[2][3] Like other trapdoor spiders, Eucteniza species construct burrows in the ground with a hinged lid, from which they wait to ambush passing prey.

The bottom of the burrow accumulates molted exoskeletons and remains of prey, which include beetles, ants, and millipedes.

Observations suggest female Pepsis seek out Eucteniza hosts and sting them in their burrows, leaving them paralyzed within.

[5] In 1895, the English zoologist and reverend Octavius Pickard-Cambridge described the new genera Favila[a] and Enrico[b] for the new species relatus and mexicanus, respectively.

[2] Both E. rex and E. stolida were synonymized with E. relata, and the previously described E. atoyacensis (Pickard-Cambridge's Enrico mexicanus) was declared a dubious name: since it was originally described based on a juvenile specimen, it is unclear whether it represents a distinct species.

Eucteniza species are distributed throughout central and northern Mexico, much of Texas, and the lower part of the Baja Peninsula.

Earlier comparisons of morphological and behavioral traits suggested the closest relative of Eucteniza is Neoapachella rothi, a forest dwelling spider found in Arizona and New Mexico,[3] while more recent studies, including analyses of DNA similarities, suggest a closer relationship to Entychides, a genus with several species ranging from Arizona to Texas into Mexico.