Moon Unit Zappa -- One Giant Leap Toward Divorce ... from Matchbox 20 Guitarist

Frank Zappa's daughter Moon Unit Zappa -- her real name -- has filed for divorce from her husband, Matchbox Twenty guitarist Paul Doucette ... TMZ has learned.

Moon Unit filed the papers in L.A. County Superior Court last week -- seeking to end her 9-and-a-half year marriage.

Moon Unit and her husband were married in June 2002, and have one 7-year-old daughter named Mathilda Plum.

Fun facts: Moon Unit also has a laundry list of acting credits, including a recent appearance on "Grey's Anatomy." Frank's other kids are named Dweezil, Ahmet, and Diva.