6:54 PM PT -- A rep for Bruce tells TMZ, the actor did indeed fracture his hip while he was on a run -- Bruce is an avid runner. We're told he's in good spirits and could be released from the hospital as early as Friday night.

Bruce Dern collapsed Friday in Los Angeles, and he's been hospitalized for a possible fracture ... TMZ has learned.

The 82-year-old Hollywood veteran was in Runyon Canyon around 3:45 PM when it happened.

L.A. Fire Dept. responded to the scene. We've learned he was transported to a hospital to be checked out for a possible hip fracture. We've got a call in to his rep for an update on his condition.

Bruce, one of Hollywood's most beloved actors and Laura Dern's dad ... has been filming Quentin Tarantino's "Once Upon a Time in Hollywood."

He just joined the cast a few weeks ago -- taking over the role of George Spahn after Burt Reynolds died last month.