Guinness World Records: Fenrir Is the World's Tallest Living Cat

Dr. Will Powers was inside the surgical suite at his medical practice when his cat Fenrir opened the door and burst into the room, looking for attention.

“I had to stop the procedure and get him out of the room,” Powers, 37, told TODAY. “After that we put up the extra lock on the door because otherwise, Fenrir can open it.”

While having a cat tall enough to open doors is an unusual problem, Fenrir holds the Guinness World Records title of “world’s tallest living domestic cat.”

Dr. Will Powers holds Fenrir, an F2 Savannah cat, the world’s tallest living cat according to Guinness World Records. Courtesy Dr. Will Powers

The 35-pound F2 Savannah cat — a breed recognized by The International Cat Association — is a cross between a domestic cat and an African serval.

Because Powers made sure many people held him as a kitten and frequently touched his paws, Fenrir developed into a friendly cat who loves meeting new friends. He thrives in his work as a therapy cat at Powers Family Medicine, his owner's medical practice, offering stress relief to patients with HIV.

Powers, a physician and HIV specialist, recently headed to a room at his office to break the news to a patient that they tested positive for HIV. Fenrir followed close behind.

“I open the door, and he immediately runs in and pops up on the exam table. The patient’s like, “The big boy!’ They’re all happy, petting him,” he said.

As Powers shared the diagnosis, the patient kept petting Fenrir. Powers explained that he is a specialist and can treat HIV with various approaches. He assured the patient they wouldn’t get sick.

The patient calmly responded, “OK, that sounds good.”

“I’ve had people break down and sob and feel like their life is over, but when Fenrir’s there, it’s just a distraction from that situation for a moment,” Powers said. “It’s calming.”

Powers designed his medical practice to incorporate his passions, like video games, geology and therapy cats. Courtesy Dr. Will Powers

Some people even request a visit from Fenrir before injections or other procedures. But the feline doesn’t let his popularity go to his head.

“He’s a big, lovable doofus,” Powers said. “He’s very, very friendly and silly. He loves to play. He jumps into stuff he’s way too big for because he just doesn’t realize how giant he became.”

Fenrir loves eating and can reach countertops, so Powers has to be careful to keep food under lock and key unless it's time for a treat. Courtesy Dr. Will Powers

At home, Fenrir is one of six pet cats. Remarkably, he is the doctor’s fourth cat to set a mark recognized by the Guinness World Records. His Maine coon, Altair, currently holds the record for “longest tail on a domestic cat living.”

Altair’s tail measures 16.07 inches – a Guinness World Record. Courtesy Dr. Will Powers

His late cat Cygnus holds the Guinness World Record for the longest tail on a domestic cat ever (17.58 inches), and another of his late cats, Arcturus, reigns as the tallest domestic cat ever (19.05 inches).

“I didn’t mean to make Guinness World Record cats, I just meant for my cats to be healthy,” he said. “And then it just happened.”

Powers credits the health of his cats to their breeder, Stacee Dallas of Starfell Savannahs in Traverse City, Michigan — who bred both Arcturus and Fenrir — and to a special diet he concocted.

All six of his cats eat a blend of raw chicken, slow-cooked meats (for easy digestion), ground-up pig bones, krill oil, feline multivitamins and other supplements.

“So it’s kind of genetics and then the combination of my diet and me being a doctor and making sure they had everything they needed to be as healthy as possible,” he said. “I put a tremendous amount of time and effort into them.”