Debra Messing Files for Divorce from Husband Daniel Zelman

"Will & Grace" star Debra Messing has filed for divorce from her husband Daniel Zelman ... TMZ has learned.

Debra cites "irreconcilable differences" in the divorce docs, filed by celeb divorce lawyer Neal Hersh in L.A. County Superior Court.

She is asking for joint custody of their 8-year-old son. She is also asking for spousal and child support -- although that could just be a formality.

The couple announced their separation last year and they stayed living together even after the separation. They were married on September 3, 2000.

Sources connected to the couple tell us they are getting along well.