Oenomaus mancha is a species of butterfly of the family Lycaenidae.

It occurs widely in wet forest in eastern Ecuador at elevations ranging from 400 to 1,100 meters.

Adult males and females are attracted to traps baited with rotting fish.

The name of the species is derived from the Spanish word mancha (meaning spot) and refers to the very distinctive, elongated black spot in ventral hindwing cell Sc+R1-Rs.

This Eumaeini-related article is a stub.