The nonprofit running the longstanding contest announced that the bear, known for his pacifist nature, was declared the winner on Tuesday with more than 100,000 votes, giving him a close win over Bear 910, with just over 50 per cent of the poll.
The contest, which is in its 12th year, celebrates the resilience of the 2200 brown bears that live in the preserve on the Alaska Peninsula, which extends from the state's southwest corner toward the Aleutian Islands.
Fat Bear Week was started in 2014 as an interactive way to inform the public about brown bears, the coastal cousins of grizzlies.
The 2025 winner, Chunk - known officially as Bear 32 - clinched his victory at an estimated 545kg.
He was handily defeated in the first round of competition this year by Bucky, who went on to lose a faceoff against Backpack, known officially as Bear 89.
All voting is done online at www.fatbearweek.org, with the public able to watch the bears on explore.org's livestream cameras before deciding on their favourite.
"Fat bears are successful bears," the nonprofit says on its website.
This group gorges itself on the abundant salmon that return to the Brooks River starting in late June.
It's there that they can stuff themselves to accumulate the fat reserves they will need to survive the winter.
Backpack is the son of former Fat Bear Week champion Holly, who introduced him to the Brooks River when he was a first-year cub in 2006.
His name was inspired by his habit of climbing onto his mother's back when they swam the river.
Fans cheered on Backpack on Instagram, noting his lineage and reputation as a gentle giant.
"Unlike many large adult male bears, Backpack hasn't shown much aggression toward his competitors," his contestant profile reads.
During winter hibernation, the bears do not eat or drink and can lose one-third of their body weight.
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