The couple were at the centre of international attention last year after it was revealed Kristen Stewart had cheated on boyfriend Robert Pattinson with Sanders, her director on Snow White and the Huntsman.
Now TMZ reports that Ross has filed paperwork for divorce in LA County Superior Court.
She is reportedly asking for spousal support, attorneys' fees and joint custody of the pair's two children, aged five and seven.
Sanders has reportedly filed a response to the divorce petition, also requesting joint custody of their children.
The pair had reportedly been in marriage counselling. Ross said in an interview in October: "I believe that we're all on journeys and we are all given lessons at certain times in our lives.
"Sometimes, when things seem really bad, you have to be able to see the good and learn from it, and just move forward as graciously as possible."
She continued: "This year was the end of some things and the beginning of something else. Beginnings and endings are always exciting."
Last week it had been reported that Pattinson and Stewart had broken up again, after initially reconciling following the Sanders affair.