Actaeus is a genus of leanchoiliid megacheiran arthropod, containing the single species Actaeus armatus.

It is known from a single specimen recovered from the Middle Cambrian Burgess Shale of British Columbia, Canada,[1] and it may be actually a poorly preserved specimen of Alalcomenaeus.

[2] The specimen is over 6 cm long and has a body consisting of a head shield, 11 body tergites, and a terminal plate.

[3] It was named after Actaeus, first king of attica, and armatus a combination of greek and latin words to describe the frontal appendages of the species.

[4]