'Charmed' Star Holly Marie Combs -- Conjures Up Divorce Papers

Holly Marie Combs -- who starred as the good witch Piper Halliwell on "Charmed" -- has filed for divorce from her husband of 7 years ... the actress confirms with TMZ.

Combs married David Donoho back in 2004 -- after meeting the guy on the set of "Charmed." David was a key grip on the show.

Combs -- who now stars on the ABC Family show "Pretty Little Liars" -- cited irreconcilable differences as the reason for the split. We're told the relationship has been rocky for "quite a while."

The couple has three young children together -- we're told Combs has requested joint custody.

As far as a prenup is concerned -- we're told they don't have one ... which could be a costly move for Combs.