The emperor penguin is the heaviest living penguin species, with adults commonly weighing about 22–45 kilograms.
Emperor penguins are also the tallest living penguins, but weight and height are separate measurements. Their large bodies help conserve heat during the Antarctic winter, when they breed on sea ice in temperatures that can fall below −40 °C.
Males and females look alike and are similar in size. The species is famous for its breeding system: after the female lays a single egg, the male balances it on his feet and covers it with a warm brood pouch while the female feeds at sea.
King penguins are the second-largest living species, so they are a common mix-up. Emperor penguins are heavier overall, while king penguins have a more colorful orange-yellow head and neck.