Chase monsters are enemies that first appear in level twenty-three of the game Magneboy.
Chase monsters are purple with a square "foot" serving as their form of movement. A siren is seen at the top of what is presumed to be their heads, and they have a tiny red circle engraved in silver above the screen, seen to be their eyes. The screen on the chase monster will have words scrolling across it: "WAIT..." for when it is asleep and "ALERT..." for when it is chasing Magneboy.
At the start of each level chase monsters are in, they will be placed at a far distance from Magneboy, far enough so that they do not chase him immediately. When Magneboy gets within three tiles' reach of a chase monster, a siren will go off, and it will begin to chase Magneboy. Sometimes they will take shortcuts to reach him in the shortest way possible, however, they move slower than Magneboy and will eventually stop chasing him if the player can successfully outrun one.