Jason Gideon is a character from the television series Criminal Minds, and is portrayed by Mandy Matinkin. He is an FBI agent who helped shape profiles and how profilers think.
Gideon is a passionate investigator and often becomes passionate about the victims. He keeps a record of all the victims he has saved. This comes back to haunt him when an unsub targets his team.
Gideon leaves the BAU when a series of events proves too emotionally devastating for him to continue on as an agent. He loses too much too quickly.
Later on in the series, we learn his ultimate fate...