EXCLUSIVE

Larry Miller -- who's starred in a TON of hit movies including "Nutty Professor" and "10 Things I Hate About You" -- is currently in the ICU at an L.A. hospital after suffering a freak injury to his head.

Miller's rep tells TMZ ... the 58-year-old actor was having a beer at an L.A. bar Tuesday after taping Adam Carolla's daily podcast show ... when he went outside to take a phone call.

On his way back into the bar, Miller lost his footing and fell backwards ... smacking the back of his head on the hard floor.

People at the scene rushed to his aid and called 911. Miller was transported to a nearby hospital ... where he was treated in the E.R. before being transferred to the intensive care unit.

We're told ... doctors have told Miller's family the actor is expected to make a full recovery, but they want to keep him in the ICU for a couple of days for observation.