The objective of this work was to identify the species of parasitic nematodes that infect the gonads of female “birdfish” Hyporhamphus naos Banford & Collette, 2001 (Hemiramphidae: Beloniformes). This species of fish is considered key in terms of the local artisanal fishery index, it is economically transcendental for fishermen and regional consumers who annually wait for its arrival in the bay to be consumed. The nematode Philometra Costa, 1845 (Nematoda: Philometridae) was identified parasitizing the female gonads of H. naos. Two immature female nematodes were found (prevalence 8%, mean abundance 0.08 and mean intensity 1). New information is recorded on the distribution of parasitic nematodes of this genus in this area of ​​the tropical Pacific and a new host. This is the first record of Philometra parasitic on female gonads in H. naos fish in Mexico. The first world recor...