The yellowtail damselfish (Microspathodon chrysurus) is a species of damselfish native to tropical areas such as the Caribbean coast of Panama. Damselfish are abundant in coral reef environments. The International Union for Conservation of Nature lists this fish as being of "least concern". The species is exploited on a minor scale, for fisheries and the aquarium trade. It may be threatened by the invasive lionfish.

Adult and young adult damselfish differ significantly in terms of body color. The difference was so stark that researchers believed the adult and young adult forms were two distinct species. Adults are brown with a yellow caudal fin. Young adults are violet with blue spots in their back and transparent caudal fins.

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