Chuck Norris has been hospitalized in Hawaii ... TMZ has learned.

Sources with direct knowledge tell us ... some medical emergency occurred in the last 24 hours on the island of Kauai that landed Chuck in the hospital. We do not know the nature of the emergency; however, we are told Chuck is in good spirits.

Whatever happened must have occurred quickly, because we're told on Wednesday he was training on the island ... a friend of Chuck's was on the phone with him, and we're told Chuck was in good spirits and cracking jokes.

The 86-year-old just had a birthday earlier this month, and he marked the occasion by posting a video on social media showing him sparring with a trainer.