Nightwing
Nightwing is a fictional superhero appearing in American comic books published by DC Comics. The character has appeared in various incarnations, with the Nightwing identity most prominently being adopted by Dick Grayson when he moved on from his role as Batman's vigilante partner Robin.
Alternative versions of Robin
It wasn't revealed until one of the later runs of the Teen Titans that this was not Dick Grayson, in fact his true identity was never uncovered. After this storyline, this version of Nightwing has not been seen since. Whether this version existed at all, after the events of Infinite Crisis or would later to be revealed to be an alternative Dick, Jason, or Tim, is unknown.