Two eyewitnesses who claim to have seen the proposal go down tell us it happened at a resort in the Bahamas. They say everyone was at a restaurant on the property doing salsa dancing when Justin's security told everyone to put their phones away, because something special was about to happen.

We're told Justin then proposed in front of everyone.

Another source with knowledge of the situation also also confirmed to TMZ that Justin and Hailey did, in fact, get engaged Saturday night.

Justin and Hailey have been almost inseparable since they began dating about a month ago. They're no strangers to each other ... they've dated before, and it appears they hooked up again just after Justin and Selena Gomez broke up.

Justin's dad, Jeremy, posted a photo of his JB Sunday with the caption, "@justinbieber proud is an understatement! Excited for the next chapter!" Jeremy himself just got hitched a few months ago.

The Biebs' mom, Pattie Mallette, also seemed to confirm the happy news on Twitter, tweeting out Saturday ... "Love Love Love Love Love Love Love."