Madoryx plutonius is a moth of the family Sphingidae. It is known from Surinam, Venezuela, French Guiana, Ecuador, Peru, Bolivia, Brazil, Argentina, Paraguay, Costa Rica and Guatemala. It is probably also present in Panama, Colombia and Guyana. Subspecies dentatus is found in Mexico and Belize.
The wingspan is 92–120 mm. It differs from all other Madoryx species in the acute forewing apex. There is a minute, circular, upper silver spot and an elongate, triangular lower silver spot on the forewing upperside.
Adults are on wing year round.
The larvae have been recorded feeding on Conostegia xalapensis and found feeding on Yemeri (Vochysia hondurensis) in Belize. Pupation takes place in a loose cocoon of yellow silk and leaves. The pupa is dark chocolate brown.