Nyssorhynchus (Nyssorhynchus) jamariensis, a new species of the Nuneztovari Complex, previously known as Anopheles (Nyssorhynchus) nuneztovari A, is described and validated using morphological characters of the adult male and female, male genitalia and immature stages. The species is recorded from the western Brazilian Amazon, where it was collected in pastures in the vicinity of the Jamari River, municipality of Monte Negro, Rondnia State, Brazil. Illustrations of the male genitalia, fourth-instar larva and pupa are provided. Nyssorhynchus jamariensis may be involved in malaria transmission, but its vector status needs further investigation.