JUSTIN BIEBER pocketed THREE trophies last night at the "American Music Awards" . . . including the night's first award, Favorite Male Artist - Pop/Rock.

--He told the crowd, quote, "I want to say this is for all the haters who thought maybe I was here for one or two years, but I feel like I'm going to be here for a very long time."

--He later performed an acoustic version of "As Long As You Love Me".  But there was no mention of SELENA GOMEZ.  In fact, Justin's date to the show was his MOM . . . whom he brought onstage for his third and final acceptance speech.

--NICKI MINAJ won TWO awards . . . Best Artist and Album in the Rap/Hip-Hop category.

--Other winners included Taylor Swift, Carly Rae Jepsen, Carrie Underwood, Linkin Park and David Guetta.

--Not surprisingly, PINK gave the best performance of the night . . . basically recreating her "Try" video.  (--You can see clips of the performance CLICK HERE.)

--PSY closed out the show with "Gangnam Style" . . . but before it was over, it turned into a DUET . . . when MC HAMMER hit the stage and the song turned into a mash-up of "Gangnam" and "Too Legit to Quit".  (-- CLICK HERE.)