The 7-year-old harlequin Great Dane from Grass Valley measured 7 feet, 1 inch when standing on its back legs.
He was diagnosed with the disease in April and had his front right leg amputated to prevent its spread. He also underwent chemotherapy as a precaution.
Gibson's owner, Sandy Hall, learned last week the cancer had spread to his lungs and spine and that no treatment that could save him. Hall decided to euthanize Gibson on Friday.
Gibson appeared on "The Tonight Show," "The Oprah Winfrey Show" and "The Ellen DeGeneres Show," and on Japanese television in 2006 after being named the world's tallest dog.
