Lethrinus erythracanthus, the orange-spotted emperor, orangefin emperor, and yellow-spotted emperor, is a species of marine ray-finned fish belonging to the family Lethrinidae. This species is found in the Indo-Pacific region.

Taxonomy Lethrinus erythracanthus was first formally described in 1830 by the French zoologist Achille Valenciennes with its type locality given as Luganor in the Caroline Islands. Some authors place the genus Lethrinus in the monotypic subfamily Lethrininae, with all the other genera of Lethrinidae placed in the Monotaxinae, however, the 5th edition of Fishes of the World does not recognise the subfamilies traditionally accepted within the family Lethrinidae as valid. The family Lethrinidae is classified by the 5th edition of Fishes of the World as belonging to the order Spariformes.

Etymology Lethrinus erythracanthus has the specific name erythracanthus which combines erythros, meaning "red", with acanthus, which means "thorn", Valenciennes described this species as having beautiful red fin rays.

Description Lethrinus erythracanthus is the largest of the 27 species in the genus Lethrinus. The body is dark brown-grey in colour with scatterd golden-orange spots. It has a short snout. Present on the body are small, light and dark stripes that appear indistinct.