Alpheus armatus is a species of snapping shrimp in the family Alpheidae, found in shallow water in the Caribbean Sea and the Gulf of Mexico.

One of the front pair of legs bears an enormous pincer, used as a hunting and deterrent weapon, which is capable of producing a loud "click".

[2] Alpheus armatus occurs in the tropical and subtropical western Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico, usually at depths greater than 10 m (33 ft).

When a potential prey approaches this shrimp, it opens its large pincer wide and advances on the intruder, snapping the claw shut with a loud click.

[2] Alpheus armatus is an obligate symbiont of a sea anemone, commonly Bartholomea annulata, and is able to acclimatise to its toxins.