Harry Styles Helps Fan With Baby's Gender Reveal At London Concert

One of Harry Styles' expecting fans got the perfect gender reveal for their upcoming baby -- courtesy of the singer himself!

Harry was rockin' out at the iconic Wembley Stadium in London Wednesday night when he spotted a fan in the crowd ... one who was holding a sign for him, asking if he'd be down to help reveal their baby's gender -- an opportunity he couldn't resist.

HS was handed a pin from the expecting mama as well as a black balloon with the question "Boy or girl?" written across it -- and the crowd, as well as Harry, went wild with anticipation.

He even shouts out, "I don't know if I'm ready!" as he teases folks with the big reveal ... but after some waiting, Harry pops it -- and reveals the lucky fan is havin' a girl!

For those unaware, Harry's been taking time out of his "Love on Tour" shows to point out some of his favorite signs he spots in the crowd ... and he's seen just about everything from a proposal to helping another girl break up with her cheating boyfriend.