Sabrina Carpenter Fans Claim Woman Dropped Pants, Peed in Middle of Pit

Sabrina Carpenter's fans must've been saying "Please, Please, Please" be warm water ... 'cause several posted on social media saying they got straight-up peed on by a fellow fan -- who unleashed her stream in the middle of the pit!

Here's the deal ... Sabrina took the stage at Chase Center in San Francisco Saturday night -- serenading the packed crowd at the arena.

While her show seemed to go off without a hitch, some fans in the pit said their night wasn't so clean ... literally, 'cause they swear a woman squatted down and took a piss right next to them.

Worth noting ... there's no video of anyone actually peeing -- but, these fans filmed the aftermath of the alleged bathroom experience, capturing a huge puddle staining the floor.

Everyone quickly moved away from it -- leaving a huge crater in the crowd. Fans could do the same if someone simply spilled a beer ... though it's a concert, and that's sorta par for the course. Urine in the pit ... a bit less common.

BTW ... this ain't just one or two fans making these claim -- a good 7 people were photographed holding up phones with the message "I Got Peed on in the Pit to See Sabrina Carpenter" written in big block lettering.

It's possible the fan just a got a little too excited and couldn't hold her bladder ... after all, she was waiting to see the newly minted 6-time Grammy nominee -- and, that's pretty dang exciting!