The Iowa native's longtime friend Phil Syracopoulos confirmed Lyon's death to The New York Times, saying only it came Thursday after years of declining health.
After starring in Lolita when she was 14, Lyon went on to act in Night of the Iguana, 7 Women, Tony Rome, Four Rode Out and Evel Knievel. Her most recent screen credits was 1980's Alligator.
The Hollywood Reporter said Lyon was married five times. Her spouses included actor-filmmaker Hampton Fancher; photographer and football coach Roland Harrison; convicted murderer Cotton Adamson; Edward Weathers; and radio engineer Richard Rudman.
Lyon is survived by her daughter Nona from her marriage to Harrison.