Rumors are swirling that the Oscar-winning actors are now engaged.
Theron, 38, was photographed wearing some new bling on a certain finger while walking through Los Angeles International Airport on Wednesday, the New York Daily News reports, sparking speculation that Penn, 53, had proposed.
The photo follows another report that says Penn, 53, and Theron are planning for more than just marriage.
"They want to get married very soon," a source told Us Weekly, and the two are reportedly planning to adopt together. Theron, already a mom to 2-year-old son Jackson, "always intended to have another child," a Penn "confidant" revealed.
Penn and Theron reportedly began dating towards the end of last year, after being longtime friends.
"Sean and I have known each other for 18 years," the "A Million Ways to Die in the West" actress told Vogue in the magazine's June issue. "We were just really good friends and it's been slow going because you are aware that you could screw that up and lose it. We had to think about it. But at the end of the day, it was somewhat effortless."
If the engagement rumors are true, this will be the third marriage for Penn. He was married to Madonna in the late 1980s, and has two children with ex-wife Robin Wright. Theron split from longtime partner Stuart Townsend in 2010.