The `Wide Awake` singer - whose divorce from Russell Brand was finalised earlier this month - was seen enjoying a romantic meal with the `Gravity` singer at the Chateau Marmont in Hollywood last night (01.08.12) and onlookers say they looked totally smitten with each other.
One source told Us Weekly magazine: "They were holding hands across the table, sneaking kisses, and laughing."
They were then pictured leaving the exclusive venue in John`s car.
However, sources the pair - who have been seen out together on a few occasions over recent weeks - aren`t serious about each and are just having fun.
A source added: "They`re just hooking up right now. It`s not serious - yet!"
Katy - who had been seeing Florence + the Machine guitarist Robert Ackroyd - recently said she was waiting for a man to woo her.
The 27-year-old pop beauty said: "I`m a woman who likes to be courted, strongly. Never say never, I guess you`d say. I`ll let love take the lead on that."
John has previously dated Jennifer Aniston, Cameron Diaz and Jessica Simpson.