*CONTAINS COPYRIGHTED MUSIC*

This is the moment a stranger got on stage during a Katy Perry concert and put his arm around the star before being swiftly removed by security.

Hannah Joy, 34, attended the concert in Sydney, Australia, on Monday (June 9) and captured the shocking moment from her spot directly in front of the stage.

Video footage shows a man appearing out of nowhere and wrapping his arm around Katy Perry's shoulders.

As soon as the pop star realises what's happening, she appears visibly startled and quickly spins out from under his arm, creating space for security to step in.

Hannah, a retail manager from Sydney, said: "I didn't see him coming. "

"I thought he was a backup dancer at first but then I realised he wasn't part of the act."

"In the video, you can see the first point of contact was a grab around the neck, which I think startled her."

"You don't know a fan's true intention."

"She moved away to give security room to intervene, and then they pulled him offstage."