A source tells Us Weekly, "Josh likes to keep things low-key, so they've just been hanging out."The acting pair was recently spotted at West Hollywood's Chateau Marmont on a double date with Seyfried's Gone co-star Jennifer Carpenter and her ex-husband Michael C. Seyfried, who split from her real estate executive boyfriend Andrew Joblon at the end of last year, previously dated actors Ryan Phillippe and Dominic Cooper, and Hartnett has been linked to a slew of stars over the last few years, among them Kirsten Dunst, Sienna Miller and Abbie Cornish.
reported that a certain source claims that Sienna Miller, who recently broke up with the actor Balthazar Getty, has found a new love.
Josh Hartnett dated Scarlet Johansson but they broke up at the end of 2006.
He was also rumored to dating Rihanna and Kirsten Dunst.
So are the single actors (she split with Jude Law in November; he most recently dated his Black Dahlia costar Scarlett Johansson) an item?
"They're friends, just friends," Miller's rep tells PEOPLE.
The source appears to be absolutely sure that Sienna and Josh are indeed dating.
More About Age: 42 Birthplace: Tarzana, Los Angeles, California, USA Profession: Musician, Model, Actor Credits: Natural Born Killers, Alias, Judge Dredd, Lost Highway Young Guns II, more Sienna Miller dated Rhys Ifans from 2007 - 2008.
The two were spotted together getting very friendly at Chateau Marmont on Tuesday night.
The third wheel didn't slow things down for the two though.
Sienna’s personal life before meeting Hartnett was quite intense.
She dated Balthazar Getty from June till November this year for whose sake she broke up with Reese Evans.