Michael J. Fox Mourns the Death of His 'Great Dog and Loyal Friend' Gus: 'We'll Miss You'

Michael J. Fox/INSTAGRAM Michael J. Fox's dog Gus

Michael J. Fox's beloved dog, Gus, has died.

The Back to the Future star, 59, announced the sad news on Monday, sharing a photo of the 12-year-old pooch on his Instagram.

"Gus — great dog and loyal friend, we'll miss you," he wrote in the caption, before referencing several pages from his 2020 memoir, No Time Like the Future: An Optimist Considers Mortality.

In addition to his tribute, Fox also posted numerous photos of himself with Gus throughout the years on his Instagram Stories.

Michael J. Fox/INSTAGRAM Michael J. Fox with his dog Gus

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Gus had been a devoted companion for Fox in his ongoing battle with Parkinson's disease. In his book, Fox called the Great Dane-Labrador mix a "wonder dog" for being a constant source of support throughout his health struggles.

"I didn't rescue Gus," the actor wrote. "You can argue that he rescued me, but he'd be too modest to make that claim."

In November, Fox spoke about how much of an impact Gus had made on his life during the CBS primetime special, The Pet Project.

"You know that no matter your situation, no matter what you feel, this animal is with you and is connected to you, and you feel," Fox, who first went public with his Parkinson's diagnosis in 1998, said. "It's a force multiplier."

Michael J. Fox/INSTAGRAM Michael J. Fox with his dog Gus

Michael J. Fox/INSTAGRAM Michael J. Fox with his dog Gus

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"Your instinct when you have a chronic illness is to sometimes isolate and make your world as small as possible so you don't have much to deal with, but a dog will open you up," he explained.

For Fox, Gus played a particularly important role in his life when he had to relearn how to walk following a 2018 surgery to remove a tumor from his spinal cord.

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According to the Family Ties alum, Gus was waiting for him by the door when he returned home from the hospital in a wheelchair.

He recalled to CBS News' Lee Cowan, "He kind of circles the wheelchair with this low kind of woof woof, woof woof, and sat in front of the wheelchair right in front of me, and looked at me, and I said, 'It's going to be okay.' "