Brad Pitt CAUGHT At Intimate Dinner With Sienna Miller

Soon-to-be single Brad Pitt is getting back in the game!

Spies spotted Angelina Jolie’s estranged hubby doing some “serious flirting” with blond bombshell Sienna Miller

during a private dinner with a group of friends as they celebrated the premiere of The Lost City of Z,

a new flick from Brad’s production company, Plan B.

Brad and Sienna — who’s starring in the adventure drama —

were “heavily enjoying each other’s company,” and “they were talking to each other all night,” says a snitch.

The encounter noticeably perked up Brad, who’s been looking scary-skinny since his stressful split from Angie.

A mole reveals the Oscar winner appeared to be “in very high spirits,

which he hasn’t been for a long time.

He seems to be over a hump.”