Tom Sizemore had a MAJOR health scare ... and now the actor is fighting for his life in the hospital.
His manager, Charles Lago, tells TMZ ... Tom was hanging out at his L.A. home around 2 AM Saturday when he suffered a brain aneurysm and collapsed into unconsciousness.
Lago says someone found Tom and quickly called 911. EMS units responded and took him to a local hospital, where he was listed in critical condition in the intensive care unit.
At this point, Tom is in a "bad way," Lago says, and his chances for a full recovery seem uncertain.
Of course, Tom has had a litany of problems over the years with drug abuse and run-ins with the law. He has been arrested for DUI, domestic violence and possession of a controlled substance.
But, he's also been a successful actor who has appeared in some of Hollywood's most popular films, such as "Saving Private Ryan," "Black Hawk Down," "Natural Born Killers" and "Heat."
Feel better, Tom. Fingers crossed.