Alex is the name of several characters in Slender Man stories. It may refer to:
- Alex Kralie - The primary antagonist of MarbleHornets.
- Alex Koval - Jeff's younger brother, and a victim of The Rake in EverymanHYBRID.
- Alex (DH) - Friend of Chris in DarkHarvest00 and a main character in the series.
- Alex in Marble Hornets - List of Alex Kralie's appearances in Marble Hornets