'One Tree Hill' Star Bethany Joy Galeotti -- I'm Divorcing My Husband

"One Tree Hill" star Bethany Joy Galeotti -- who plays Haley on the show -- is calling off her marriage to her musician husband Michael Galeotti ... and says she's already mentally preparing to ditch his last name.

Bethany made the announcement on her blog ... writing, "I'm sorry to say that Michael and I have decided to divorce. We remain friendly and dedicated to raising our beautiful girl."

She continued, "The only reason I'm saying anything about this at all is because you'll all be wondering soon why everyone is calling me 'Bethany Joy Lenz' again."

The two married in 2005. Bethany gave birth to their daughter Maria, their only child, in February 2011.