Following the Oscar winning duo's relaxing vacation over the holidays, the rumored couple was spotted out and about together in and around Los Angeles.
The esteemed actors were first spotted leaving Theron's Hollywood Hills, Calif. home the morning of Jan. 2, and although they left the home in two separate cars, a source tells E! News, they went back to her home and spent the night together Thursday night.
The pair emerged together Friday, with Theron behind the wheel of her black Lexus and Sean in the passenger seat, as they headed out for an hour-long drive to Penn's Malibu home, where they spent the remainder of the day.
While Penn took a sunset jog around the beach community that day, the actress stayed in the home and relaxed with her dog.
Saturday, the duo was spotted hitting Starbucks in Los Angeles, with Theron grabbing three cups of coffee and then hopping in the car with Penn, who was waiting for her in the driver's seat of her Lexus.
The actors' reps had no comment on the nature of their relationship when E! News reached out for clarification.
Theron and Penn have kept mum as well.