Phanaeus dionysius is a species of dung beetle in the family Scarabaeidae.

It is found in region of San Pablo Etla of Oaxaca, Mexico.

[1] The specific name dionysius is named after Dionysius II of Syracuse, main character of moral anecdote of the “Sword of Damocles”.

Body dull shiny black with a faint blue luster.

Slender, long horn strongly curved.