In collections of ectoparasites from 368 small ground finches, Geospiza fuliginosa, in populations from the islands of Isabela, Santa Cruz, San Cristóbal, and Santa Fé, in the Galápagos Archipelago, Ecuador, we found 8 species of mites. Four mite species were common on all islands sampled, i.e., Mesalgoides geospizae Mironov and Pérez (Psoroptoididae), Xolalges palmai Mironov and Pérez (Xolalgidae), and 2 new species, Trouessartia geospiza n. sp. (Trouessartiidae) and Proctophyllodes darwini n. sp. (Proctophyllodidae). Four other species were represented by single collections from G. fuliginosa, i.e., Pterodectes atyeoi n. sp. (Proctophyllodidae), Strelkoviacarus sp. (Analgidae), Dermoglyphus sp. (Dermoglyphidae), and Dermanyssus sp. (Dermanyssidae). Authorship of new species names is attributed to the 3 authors who prepared the descriptions (B.M.O.C., J.F., D.L.). Trouessartia geospiza and P. atyeoi were also found on previously collected specimens of other Geospiza species in museum collections. For the 4 common species, we found no differences in prevalence among the 4 island populations, but infection prevalence differed among the 4 species. The mean infection prevalence was high for T. geospizae (89%), moderate for M. geospizae (58%) and X. palmai (44%), and low for P. darwini (26%) in all populations. The feather mite fauna of G. fuliginosa was similar to that of other Geospiza species, and generally related to communities found on other emberizid finches.