Stewie was surrounded by family when he succumbed to a yearlong battle with cancer Monday evening at his Reno home, owner Robin Hendrickson said. He was 8.
Guinness World Records declared Stewie the record-holder in August 2010, measuring 48.5 inches (1.23 meters) from the tip of his nose to the tip of his tail.
Hundreds of fans flooded Stewie's Facebook site with memories and condolences. The Maine Coon cat was a certified therapy animal that frequently visited a Reno senior center and helped promote animal welfare awareness with the Nevada Humane Society.
"Stewie was always very social and loved meeting new people," Hendrickson said. "He has touched many lives, and for that I am grateful."
Stewie's full name was Mymains Stewart Gilligan. Hendrickson bought him from a breeder in Hermiston, Oregon, in 2005. He attended the International Cat Show in Portland, Oregon.
"He did well at the show, even though he wasn't feeling perfect," said Valerie Horton, the show's entry clerk. "He loved being there because he loved the public. He always did."