Patriots Cheerleader -- BLOWS J.LO AWAY ... On 'American Idol' Audition

The Patriots have ANOTHER thing to be pumped up about ... one of their cheerleaders appeared on "American Idol" last night ... and KILLED IT.

22-year-old Stephanie Petronelli stepped in front of Jennifer Lopez, Keith Urban and Harry Connick Jr. during the Boston auditions and belted out Grace Potter’s “Paris (Ooh La La).”

The Patriots tell TMZ Sports ... Stephanie had to get permission from the team before she could appear on the show in her official cheer uniform -- and the Patriots were happy to give their blessing.

J.Lo dug it ... Keith was on the fence ... and Harry told her she sucked.

But just like the Patriots, Stephanie found a way to get to the next round.

And get this ... the Patriots have been SWORN to secrecy about Stephanie's fate on the show. A rep for the team tells us producers have specifically asked them to stay mum on the cheerleader so they won't give away the results for the next round.