Morgan Wallen's got an arm on him -- the country superstar was caught on video ripping a phone out of a security guard's hand and launching it across the stage during a concert in Pittsburgh.

The bizarre moment went down Friday night at Acrisure Stadium ... with footage showing Wallen spotting the guard holding up a cellphone near the stage before suddenly grabbing it and chucking it away mid-show.

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Fans who witnessed the incident reportedly claimed the phone wasn't being used by the guard for personal reasons -- instead alleging he was helping record video for someone in the crowd. Either way, Wallen didn't seem thrilled about the device being pointed in his direction.

Looks like stage props aren't the only things flying at his shows these days -- just a week after he flipped a piano during a Denver concert, he's now gone viral for launching a cellphone across the stage.

The incident came just one day before Wallen canceled his second scheduled Pittsburgh concert due to weather concerns ... as we reported, it was a decision that generated plenty of backlash from disappointed fans.

First a piano, now a cellphone ... Morgan's got us wondering what might go airborne next!