Mary Tyler Moore -- the television icon who charmed America with comedic brilliance and charisma on her hugely successful '70s show -- died in a Connecticut hospital ... TMZ has learned.

MTM's longtime rep, Mara Buxbaum, issued a statement to TMZ saying, "Today, beloved icon, Mary Tyler Moore, passed away at the age of 80 in the company of friends and her loving husband of over 33 years, Dr. S. Robert Levine."

"A groundbreaking actress, producer, and passionate advocate for the Juvenile Diabetes Research Foundation, Mary will be remembered as a fearless visionary who turned the world on with her smile."

We're told Mary had been on a respirator for more than a week.  She was taken off life support Tuesday night.

Mary -- who battled diabetes and underwent brain surgery in 2011 -- became famous after starring on the "The Dick Van Dyke Show" from 1961 to 1966. She dazzled her way to 7 successful seasons on "The Mary Tyler Moore Show" from 1970 to 1977, decimating skeptics who viewed her show as destined to fail.

MOORE HERE