What mammal has the longest lifespan of any mammal?

The mammal with the longest known lifespan is the bowhead whale. These Arctic baleen whales can live for more than 200 years, with age estimates for exceptional individuals reaching roughly 211 years or potentially higher.

Bowhead whales spend their entire lives in Arctic and subarctic waters, where their enormous bodies and thick blubber help them survive freezing conditions. They feed mainly by filtering tiny organisms such as krill and copepods through exceptionally long baleen plates. Their slow growth, late maturity, and long reproductive lives are characteristic of an animal built for extreme longevity.

Scientists have estimated bowhead ages using several clues, including chemical analysis of eye tissue, growth structures, and old harpoon fragments found embedded in harvested whales. A nineteenth-century harpoon in a bowhead suggested that the animal had survived for many decades after being struck. Humans can occasionally live past 100, and some elephants reach their 60s or 70s, but neither approaches the bowhead's documented longevity.