The alfonsino or alfonsin (Beryx decadactylus) is a deepwater fish of the family Berycidae that inhabits temperate and tropical ocean waters nearly worldwide, with the exception of the eastern Pacific. More generally, the name is also used to denote any member of the family Berycidae.

Alfonsinos have large eyes and deep, compressed bodies. They have a rose red color, and orange below, with all fins and the inside of the mouth bright red. This is a common adaptation to deepwater surroundings, where red is filtered out of the light spectrum. They have a maximum length of 60 cm.

This and several other species of the genus Beryx, like the splendid alfonsino are commercially harvested throughout the world, often distributed under the names of imperador, red bream, and Tasmanian snapper.