Pristionchus is a genus of nematodes (roundworms) in the family Diplogastridae that currently includes more than 50 described species.

They are known mainly as non-parasitic associates of insects, especially beetles, while others have been reported from soil, organic matter, or rotting wood.

The genus includes P. pacificus, a satellite model organism to the well-studied nematode Caenorhabditis elegans.

In Pristionchus species associated with insects, the nematodes usually live on their hosts in a dormant stage (the dauer larva).

[2] Most species of Pristionchus show a polyphenism in their feeding structures, which allows the nematodes to access different food resources in this rapidly changing environment.