Justin Bieber was straight up BOOED at the Billboard Music Awards last night … and not like 1 or 2 people … it was a straight up CHORUS of boos … and it made Justin super uncomfortable.

It all went down when Cee Lo called on Bieber to receive the first ever Milestone Award — but when Bieb got to the stage, the crowd turned on him.

Of course, there were some screams from the hardcore Bieber fans … and JB managed to silence the haters for a minute by thanking Jesus Christ (who’s gonna boo JC?) … but overall, more boos than a haunted house.

As for the Bieber/Selena Gomez situation, the two were NOT seated together during the show — despite a pre-show photo of the seating arrangement that suggested they would be.

Instead, she was kickin’ it with Taylor Swift … and didn’t stand when Bieber’s name was called for the Top Male Artist Award.

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