Marion Barber III -- former Dallas Cowboys running back -- was arrested in Texas yesterday ... TMZ Sports has confirmed.
According to police records, Barber was arrested just after 8PM on Sunday night -- and he's being held for "mental detention and observation."
So far, it's unclear exactly why Barber was arrested. We're workin' on it.
31-year-old Barber played in the league from 2005 to 2011 -- all but one year with the Cowboys. He spent his final season with the Chicago Bears ... and retired in 2012.