Three species of Belostoma Latreille, 1807 (Insecta, Heteroptera) were found to be intermediate hosts of digenetic trematodes of the genus Stomylotrema Looss, 1900, parasitic in birds. Several infected specimens of Belostoma elegans (Mayr, 1871) and Belostoma oxyurum (Dufour, 1863) were collected in the Arroyo Zapata, Province of Buenos Aires, Argentina; one infected specimen of Belostoma foveolatum (Mayr, 1863) was found in the Arroyo Cuña-Pirú, in the Province of Misiones. Encysted metacercariae were found mainly in the abdominal cavity of adult male and female belostomatids, with low prevalences and variable intensities of infection. Species of Belostoma are reported for the first time as intermediate hosts of digenetic trematodes and as new intermediate hosts for representatives of the genus Stomylotrema. Natural infections of adult Stomylotrema spp. were found in several insectivorous birds present in the Buenos Aires study area. The role of other aquatic organisms as intermediate hosts of Stomylotrema spp. is discussed.