Aristotelia Hübner, [1825] (Lepidoptera, Gelechiidae, Aristoteliinae) is a widely distributed moth genus comprising 153 described species, many of which have striking forewings. The variation in genitalia morphology among some members suggests that, as currently circumscribed, the genus is probably not monophyletic. The only Chilean species of Aristotelia previously described inhabits the central region of the country. A second Chilean representative, Aristotelia aguilensis sp. nov., is described and illustrated based on adults reared from larvae collected on Hoffmannseggia minor (Phil.) Ulibarri (Fabaceae) in the Atacama Desert. The genetic divergence between DNA barcode sequences of the new species was 0.3% (K2P), while it ranged from 11% to 17.1% for other members of the genus. This study reveals a new piece of the Aristotelia puzzle, adds a new member to the poorly known gelechiid fauna of northern Chile, and highlights the need to continue fieldwork to reveal the moth diversity that remains overlooked in underexplored Neotropical environments.