Angelina's not going to like this!

Brad Pitt and Sienna Miller have been the subject of romance rumors for months, and although the British actress has denied it, Us Weekly is claiming there really IS something going on between them. "They’ve been spending some time together," a source dished to the mag.

The two were first reported to be getting cozy back in April, after eyewitnesses spotted them flirting at an intimate dinner for their upcoming film. At the time, the American Sniper beauty was quick to squash the chatter. "I'm not going to even dignify it with a response. It's predictable and silly," she told Page Six at the time.

It got a little harder to pull the wool over everyone's eyes when they were caught making out at the Glastonbury music festival in June.

"Brad and Sienna couldn't keep their hands off each other, touching and stroking each other at every opportunity. They seemed really intimate. They seemed keen to get away from prying eyes and made a dash for the Rabbit Hole, the festival's underground and exclusive venue, with a group of friends and were inseparable as they waited to go inside," a source dished to The Sun.

"The party was cut short and they had to leave after five minutes because the venue was closing. Bradley Cooper left and Brad and Sienna headed back arm in arm to their private Winnebego," the source added.

This is the actor's first "relationship," if we can call it that, since he split with Angie this past September. We wouldn't want to be the girl that moves in on Angie's man!