Madonna Performs with Sabrina Carpenter in Lingerie On Coachella Stage

Sabrina Carpenter's fans must have thought they were seeing double at Coachella Friday -- but they weren't, 'cause it was Madonna!

That's right ... The "Material Girl" herself popped up onstage with Sabrina near the end of Sabrina's set during the second weekend of Coachella. 

From underneath the stage, Madonna suddenly appeared with her back to the crowd, then launched into her dual performance with Sabrina. The two cranked out a few of Madonna's legendary hits, namely "Vogue" and "Like A Prayer."

Both singers looked like twin sisters decked out in their hot outfit choices ... Madonna, BTW, opted for some purple, sexy lingerie, and they had similar blonde hairdos while commanding the stage together.

As for the crowd, they went completely berserk ... singing along to the tunes while watching these 2 music icons together on stage.

For Madonna ... the performance marked her return to Coachella for the first time in over a decade. You may recall, she made a similar cameo during Drake's set in 2015, and was a headliner at the festival in 2006.

And that's not all ... the "Queen of Pop" has a new album -- "Confessions II" -- which will be coming out soon. Fans are certain Sabrina is on the album ... but no solid confirmation on that, yet.