The Oscar winners rang in the New Year together in Hawaii, a source confirms to PEOPLE.
Theron, 38, made a trip to the island without her son, Jackson, 2, to celebrate the holiday by staying at Penn’s beachfront home in Oahu.
Before the clock struck midnight, Penn, 53, spent Tuesday afternoon surfing in the Pacific while the Prometheus star soaked up the sun in a multicolored striped bikini. Later the pair met up with a male friend and sat in the sand, enjoying the water view.
On Wednesday evening, the two were spotted stepping off the same flight at LAX airport. On Thursday, Theron and The Secret Life of Walter Mitty actor both left her house in separate cars, a source reveals.
“Charlize and Sean have been friends for years,” says another source. “They have been spotted out together several times in the past few years. Even when Charlize was dating Stuart [Townsend]. They both had dinner with Sean several times.”
Rumors of a romance between the two first flared up in 2010 after Theron split with Townsend. Most recently, the two were seen acting very flirty at Seth MacFarlane‘s Halloween party last October.
“They were laughing and touchy-feely,” says a source.