Britney's First Hubby Locked Up

Jason Alexander -- the dude who married Britney for 55 hours back in 2004 -- is currently sitting in a Van Nuys jail cell.

According to the L.A. County Sheriff's Department, 27-year-old Alexander is set to be released on December 9.

Here are some fun facts courtesy of the cops: Alexander is 6'0", 225 pounds with black hair and brown eyes.