Mary-Kate Olsen is reportedly back together with former boyfriend David Katzenberg.

Billionaire Olsen, who dated Katzenberg for nine months in 2004, later went out with Stavros Niarchos. She was heartbroken when she found out Niarchos had moved on to date Olsen's ex-friend Paris Hilton.

However, according to Sky Showbiz, Olsen is back with Katzenberg thanks to a series of romantic dates.

"They were leaning close together, touching hands and stuff and only had eyes for each other - and they were big, gooey doe eyes at that," revealed an onlooker. "From what I could tell, they're very much a couple."