Citing irreconcilable differences for the split, the actress has retained the services of powerhouse divorce attorney Laura Wasser as she prepares for a court battle over custody of her daughter Sam and unborn baby.
The couple's daughter is a year old, and Richards is six months pregnant with their second child.
In the legal papers, filed in Los Angeles on Mar. 1, Richards also demands "miscellaneous jewelry (corr) and other personal effects," as well as "earnings and accumulations of Petitioner from and after the date of separation".
The divorce comes completely out of the blue for the couple, who seemed to be perfectly happy when they were recently interviewed about their new baby news.
Richards even joined her husband on his hit TV show Two & A Half Men late last year.
And in October, Sheen confessed he had had tattoos lasered off his chest to prove once and for all he had turned his back on his hedonistic past.
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He said, "I had some tattoos lasered off my chest. They don't represent the lifestyle I thought I would always have."
And just last month, Sheen made no mention of any marriage trouble when he told American magazine Us Weekly that he couldn't wait to become a dad again, and confessed he and Richards were hoping their second child would be another girl.
Sheen announced the couple's engagement at 2002's Golden Globe Awards after proposing to the actress in Hawaii.
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