Capillaria is a genus of nematodes in the family Capillariidae (or Trichinellidae, according to some classifications).

The taxonomy of the Capillariidae is disputed, with species included within either the single genus Capillaria or 22 different genera (Amphibiocapillaria, Aonchotheca, Baruscapillaria, Calodium, Capillaria, Capillostrongyloides, Crocodylocapillaria, Echinocoleus, Eucoleus, Freitascapillaria, Gessyella, Liniscus, Paracapillaria, Paracapillaroides, Pearsonema, Paratrichosoma, Pseudocapillaria, Piscicapillaria, Pseudocapillaroides, Pterothominx, Schulmanela, and Tenoranema).

The term capillariasis is generally used for diseases produced by all species currently or formerly classified in this genus.

Some species parasitic in fish, previously classified within Capillaria, are now included in Huffmanela (family Trichosomoididae).

This Enoplea nematode (or roundworm-) related article is a stub.