George Kennedy, star of "Cool Hand Luke" and the 'Naked Gun' movies, has died at the age of 91 ... TMZ has learned.

George's grandson Cory Schenkel says Kennedy died Sunday morning at 4:30 AM in Boise, ID. He says his grandfather had been in failing health ever since his wife Joan died a little over a year ago. George had been under hospice care for the past month.

Kennedy won the Best Supporting Actor Oscar in 1968 for "Cool Hand Luke." He also starred in all 3 of the 'Naked Gun' flicks, "Airport 1975," "Earthquake" and many many more.