Now the identity of his mystery girlfriend may be revealed: Public records suggest Oksana Grigorieva, 39, an ex of former James Bond star Timothy Dalton, has lived in a house linked to Gibson, 53.
The home, purchased in Sherman Oaks, Calif., in December 2008, has an ownership trust administered by the CFO of Mel Gibson's production company, Icon.
While neither Grigorieva nor Gibson have commented, Grigorieva certainly resembles the leggy brunette photographed with Gibson on the Boston set of his upcoming film, Edge of Darkness, and seen frolicking in the surf with the star in Costa Rica.
A composer, Grigorieva is dedicated to her craft, her former agent Victor Kruglov tells PEOPLE. "She'll never give up with her music," says Kruglov, who has seen photographs of Mel's mystery woman and believes she and Grigorieva are one and the same. "She loves it."
Though she rarely confided in him about her love life, Kruglov says Grigorieva did once complain about trouble with a boyfriend – but stopped short of sharing specifics. "She was always very discreet about her personal business," he adds.
She has one son with the 63-year-old Dalton, Alexander, who is based in Los Angeles.
The Other OksanasBefore Grigorieva entered the picture, no fewer than three "Oksanas" were fingered as Gibson's Russian doll, sparking an international mystery befitting 007's skills:
Almost immediately after Gibson's divorce proceedings hit the news, media reports ID'd her as Oksana Kolesnikova, a pianist and composer who performs five days a week at the Beverly Hills Hotel's Polo Lounge.
There's just one problem: Kolesnikova, a blonde, has been happily married for 10 years and is four months pregnant. "I have nothing to do with [Gibson]," the singer tells PEOPLE. "The only contact I had with him was when he came in to dine at the Polo Lounge. He seemed like a gentleman."
Days later, Russian pop star Oksana Pochepa, 24, came out of the woodwork and told British newspapers that she's the one dating Gibson – and is the woman seen in photos hugging him in Costa Rica.
"This is serious and I hope that our union will be real and strong and long-lasting,” Pochepa told the Sun tabloid of her alleged relationship with Gibson. However, Pochepa doesn't look much like the woman in the photos taken in Boston.
Meanwhile, back in January, the Latin American Herald Tribune ran a photo of yet another Oksana – Oksana Lovoushka, a blonde artist the paper says was in Mexico with Gibson in January filming her music videos. Lovoushka, too, hasn't commented.
With reporting by ANN COCCAGNIA