Oh my. Per TMZ: Recently-axed UFC fighter Jason "Mayhem" Miller was arrested today in Orange County, TMZ has learned -- after allegedly breaking into a church, spraying a fire extinguisher all over the place, and getting buck naked.

Law enforcement sources tell TMZ, the O.C. Sheriff's Office received a call early this morning from the Mission Hills Church in Mission Viejo about a possible burglary in progress.

When the deputies arrived, we're told they found the first and second floors covered in white fire extinguisher spray. Cops say the place was also trashed -- scattered CDs, books, and broken pictures.

When officers reached the second floor, we're told they found Miller naked on some couch -- totally awake and coherent.

This just doesn't seem like conduct consistent with the "Mayhem" nickname, but it sounds like they have solid evidence so we'll have to believe it.