A new species of Neotropical Hydrochus, H. spanglerorum n. sp., is described, based on specimens collected in Brazil, Guyana, and Suriname. The new species has unusual external and male genitalia morphology, which are described, discussed and illustrated. Among other unusual characters, the males have markedly pitted and iridescent femora, and the male genitalia have the parameres and basal piece fused, and the aedeagus dorsal basal lobe located near the distal end of the male genitalia.