Jonathan Cooper is behind bars in a Colorado jail ... after the standout Broncos linebacker was arrested Thursday night around 11 PM, TMZ Sports has learned. It's unclear what led up to the arrest, but the 6th-year pro is being held on two counts…

A fan interrupted Game 1 of the NBA Finals in hopes of getting a selfie with Victor Wembanyama ... with the unwelcome guest rushing the court and approaching the San Antonio Spurs superstar with his phone before getting yanked away by security. The…