Justin Bieber HAS BEEN BEHAVING ... Says NFL Star Neighbor

Good news Beliebers ... your fearless leader has been a GOOD BOY recently, so says one of his famous Calabasas neighbors.

TMZ spoke with retired NFL stud Willie McGinest -- who lives right near Justin Bieber in the ultra-exclusive gated community where the singer gained his reputation as the WORST NEIGHBOR EVER.

But Willie says things have quieted down since the infamous Justin vs. Keyshawn neighborhood war ... and even JB's entourage (Lil Twist and Lil Za) have been staying out of trouble.