The Slender Man (also spelled Slenderman) is a fictional supernatural character that originated as a creepypasta Internet meme created by Something Awful forum user Eric Knudsen (also known as "Victor Surge") in 2009. He is depicted as a thin, unnaturally tall humanoid with a featureless white head and face, wearing a black suit. Stories of the Slender Man commonly feature his stalking, abducting, or traumatizing people, particularly children.
https://en.wikipedia.org/wiki/Slender_Man