Ex-UFC Fighter Jason 'Mayhem' Miller -- Charged with Vandalism After Naked Church Arrest

Jason "Mayhem" Miller has been charged with vandalism after allegedly breaking into a church, getting buck ass naked, and trashing the place ... this according to the Orange County District Attorney.

According to the charging docs, obtained by TMZ, Mayhem was hit with one misdemeanor count of vandalism -- and if convicted, he faces up to a year in jail.

In the criminal complaint, the D.A. claims Miller "did maliciously and unlawfully deface with graffiti and other inscribed material, damage, and destroy church property ... in the amount of $400 and more."

TMZ broke the story ... Mayhem was arrested last month inside the Mission Hills Church in Mission Viejo. Cops say Mayhem was totally naked, reclining on a couch, when they found him.

Cops also claim Mayhem trashed the place, scattering books, photos, and breaking CDs. He also allegedly unleashed a fire extinguisher all over the place.

Mayhem is due in court November 21st.

Calls to Mayhem's reps were not immediately returned.