Who is the young celeb that faces a serious death threat?

46-year-old Thomas Brodnicki -- a man with a criminal history of stalking -- allegedly told his shrink he was going to kill Selena Gomez.

According to the declarations of Selena and her lawyer, Blair Berk.. Brodnicki told the shrink he traveled from Chicago to L.A. to meet her, visited her workplace at least 3 times and has told people he had conversations with God about killing her.  Selena says she is in "extreme fear," believing he will carry out his death threat against her if he isn't stopped.

Selena and her lawyer claim Brodnicki was picked up for mental evaluation last month after he allegedly threatened to "scratch people's eyes out on the street."  Brodnicki allegedly made the threats against Gomez during his mental evaluation.

According to court docs, LAPD detectives are taking the threats "extremely seriously" because of Brodnicki's history of mental illness and making criminal threats.