Selena Gomez -- Intruder Arrested Outside Her House

Scary moment for Selena Gomez that had nothing to do with Justin Bieber -- instead it was a guy getting busted at her home for allegedly creeping around on her property Saturday morning.

Cops rushed to Selena's crib after a family member inside called 911 and said they spotted a young man lurking on the property ... this according to law enforcement.

It's unclear if Selena was home at the time, but the 19-year old man allegedly told cops he was there to see the singer in person.