A new species of the genus Benthoctopus is described and illustrated based on 14 specimens collected from the coast of Central Chile and the Juan Fernández Archipelago, at depths between 436 and 1000 m. This medium sized species (total length between 425 and 770 mm) has no ink sac and presents the following attributes: small biserial suckers; large eyes (diameter between 11 and 23 mm); the first pair of arms longer than the other arms; 63 to 75 suckers in the hectocotylized arm; eight to nine lamellae per demibranch and a W-shaped funnel organ. This new species, which we call Benthoctopus longibrachus, is compared to other species in the genus.