Katy Perry and John Mayer were reportedly all over each other at a recent party.

The pop singer has had an on-off relationship with Hollywood lothario John since they got together earlier this year.

The couple went to Hello Giggles blogger Sophia Rossi and New Girl creator Liz Meriwether’s joint birthday function in Hollywood on November 10.

Katy and John looked absolutely enamoured with one another

"[They were] so affectionate," a source told Us Weekly.

"John had his hand on Katy's back a lot, and they were kissing and holding hands."

It is rumoured that Katy and John split temporarily, but it appears that the pair’s romance is going strong.

“[They are] full-on dating,” the source revealed.

Katy took a few moments away from smooching John to speak with her friends at the bash.

Jon Hamm, Nicole Richie, Shannon Woodward, Mindy Kaling and Zooey Deschanel were also in attendance.

"Katy and Zooey were joking about how they look alike," the insider said.

The American singer is divorced from British comedian Russell Brand after a 14-month marriage. Since then she has been linked to Florence + the Machine guitarist Rob Ackroyd and most recently John.