Aristillus is a prominent lunar impact crater that lies in the eastern Mare Imbrium.
The rim of Aristillus has a wide, irregular outer rampart of ejecta that is relatively easy to discern against the smooth surface of the surrounding mare.
This is the protruding rim of an old crater that has been almost completely submerged by the lava flows of the surrounding Mare Imbrium.
English progressive rock band Camel named the first song on their album Moonmadness after the crater.
By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Aristillus.