"Yes, I have filed for divorce," the actress, 45, tells PEOPLE in the latest issue, in which she also reveals she has adopted a son, 3½-month-old Louis.
A rep for Bullock confirms the star filed legal papers seeking to end her marriage, but declines to specify in what jurisdiction they are filed. Says Bullock of her decision to divorce: "I'm sad and I am scared."
It was a cheating scandal that rocked the couple's marriage, with several women claiming to have had illicit affairs with James, 41.
The motorcycle mogul, who has publicly apologized to Bullock and his three kids, recently returned home after a 30-day stay in a treatment facility where he sought help for "personal issues."
For much more on this story – including photos of Bullock with Louis and an emotional interview about her breakup with James and her life as a new mom – pick up the new issue of PEOPLE, on newsstands Friday