The determined mutt fiercely stood tall when the giant bear approached, forcing it to retreat and trudge into the distance.
Keen photographer Alberto Panizza, 39, captured the incredible moment while visiting Churchill in Manitoba, Canada, earlier this month.
The snapper revealed the fiery pooch was approached by the bear and reacted in a startling frenzy as soon as it sensed danger.
The dog - chained up to stop it escaping - was owned by a local breeder who claims his dogs, used to pull sleds, are the strongest in the world.
Alberto, from Parma, Italy, told Caters News: "The dogs live not far from a town where polar bears often pass through.
"This one seemed to be curious and even though much bigger it was eager to make acquaintances with the dogs.
"Even if they are trained to fight bears, the dogs usually seem afraid.
"But either due to their survival instinct, or pure madness, they sometimes throw themselves at the wild giants like this one did."
However, it's not always bad blood between polar bears and dogs. A BBC Two programme, Nature's Weirdest Events, showed that polar bears visit Eskimo dogs ever year in Canada's Hudson Bay - just to play with them. Awww.