Casey Affleck's Wife Files for Divorce

Casey Affleck's wife of 9 years, Summer Phoenix, is filing for divorce, and according to her the split's been a longtime coming.

Summer filed the divorce petition Monday in Los Angeles ... citing irreconcilable differences. The couple has 2 sons -- 13-year-old Indiana and 9-year-old Atticus. In the docs, she requests joint physical and legal custody of the boys.

In the docs, she lists their date of separation as November 2015 -- although they didn't announce the split until March 2016. Point is... things had long since been on the rocks when Casey won the Oscar for Best Actor earlier this year.

Summer is asking for spousal support and attorney fees.