If this is true, they'd be Hollywood's hottest new couple!

Rumors are swirling that Brad Pitt and Charlize Theron are hooking up ... and we could totally see it! The dynamic duo posed for a Breitling watch campaign six months ago and that's when sparks flew, according to multiple reports. Pitt, 55, and Theron, 43, were even reported to have been introduced by Charlize's ex Sean Penn -- a claim which has also been shot down. The Sun reported the two spent Christmas together, but both are so low-profile, there hasn't been any photographic evidence. The two ARE neighbors, which is interested - check out HIS home and HERS.

Brad was dating MIT professor Neri Oxman last year, but things between them cooled. And the actor-artist has been dealing with his divorce from Angelina Jolie and custody proceedings regarding his kids.

Speaking of his offspring ... we spotted his and Angelina's biological children twins Knox and Vivienne, 10, and Shiloh, 12, at a local LA pet store over the weekend, accompanied by a bodyguard and a driver. Pitt reportedly spent time with all his kids over the holidays. Maybe blending his tribe with Charlize and her two adopted children August and Jackson? Sounds fun!