anistontherouxdinner.jpgTheroux photo courtesy NBC

X17online can report exclusively that Jennifer Aniston and Your Highness star Justin Theroux enjoyed a romantic dinner date Wednesday night at West Hollywood's Sunset Towers Tower Bar.

A source tells X17 this isn't a first date for the couple -- they've been hooking up for a while:

    "Jen and Justin have recently started dating. They've known each other for a while, but they're more than friends now. They're cautious -- they're both taking it slowly."

Theroux -- who has had parts in the TV show Parks and Recreation and in films like Tropic Thunder, Zoolander, Mulholland Drive to name a few -- arrived at Jen's favorite restaurant separate from Aniston and the couple stayed from about 7 - 10 pm. After a three-hour dinner, they decided to leave together, but they didn't make it easy for us to get a shot!

They exited from the underground parking lot with a chauffeur in the driver's seat, while they ducked down in the back. The car took them back to Aniston's Beverly Hills mansion.

Aniston hasn't had a serious boyfriend since John Mayer in 2009. Will this relationship last?