Olivia Rodrigo Rocks Out To 'Good 4 U' At Phillies Game

Olivia Rodrigo turned the Philadelphia Phillies game into her own prom on Thursday ... dancing her face off and vibing to her hit song!!

The moment was captured on the Citizens Bank Park scoreboard in the 6th inning of the Phils' game against the New York Mets ... with the stadium showing off the Grammy winner to the fans.

Naturally, OR's "good 4 u" was blaring over the speaker system ... and just like the rest of the world does when they hear it (admit it, you love it), the singer had to rock out.

The video is pretty cool -- Rodrigo jumps up and down, waves to the cameras, dances and points out her friends as the crowd loses it.

So, what the heck was she doing at a Phillies game?? Rodrigo is in the City of Brotherly Love the next two nights for her "SOUR" tour ... so why not catch a good ol' ballgame??

But, by the looks of it, Olivia might not have cared too much about the action on the diamond ... as she was spotted taking pics during the middle of the game.

Hey ... when ya got 25 million followers on Instagram, you gotta take advantage of every photo op.

As for the game, the Phillies lost 8-7 ... and it was one of the biggest collapses in team history.