The emperor penguin is the biggest penguin. A grown emperor penguin stands about 1.1 meters (45 inches) tall. A big emperor penguin can weigh about 40 kilograms (88 pounds). The king penguin is the second largest penguin. The gentoo penguin is the third largest penguin. The little penguin is the smallest kind of penguin. Penguins as big as or bigger than emperors lived between about 50 and 20 million years ago. A fossil penguin named Kumimanu biceae stood about 1.65 meters tall and weighed about 100 kilograms. The Kumimanu fossil is about 55 to 60 million years old, close in age to the oldest known penguins.

Emperor penguins breed in the middle of the Antarctic winter. Emperor penguins build up fat before winter and live on it while they fast during breeding. Emperor penguins breed on sea ice and also hunt along its edge, so they depend on it. Most emperor colonies sit on fast ice, sea ice that is frozen to the land or to grounded icebergs. Emperor penguins rely on stable fast ice for about eight months of the year, from breeding until chicks leave. Many penguins live in big groups called colonies, some with thousands or even millions of birds. Penguins huddle close together to stay warm.

Early sea ice breakup can be deadly to chicks: in 2016 more than 10,000 emperor chicks died at one colony when ice dissolved too soon. As of April 2026, satellite images show about a 10 percent loss of emperor penguins across Antarctica between 2009 and 2018. As of November 2026, climate change is the main cause of the fall in emperor penguin numbers. As of November 2026, emperor penguins are officially listed as at risk of extinction: threatened under the United States Endangered Species Act and Endangered on the IUCN Red List. As of November 2026, the main reason is shrinking sea ice, which is expected to keep shrinking for decades.

People once took penguin eggs for food, which hurt some penguin populations. Penguins are protected by law from hunting and egg collecting. The Antarctic Treaty System protects Antarctic penguins; harming a penguin or its eggs is illegal there. As of November 2026, about two-thirds of the 18 penguin species are listed as threatened by the IUCN. As of November 2026, the Galapagos penguin is endangered. As of November 2026, African penguins are critically endangered, and their numbers have been falling since the early 1900s. Penguins are indicators of the health of the ocean and of climate change. Dangers from people include oil pollution, fishing nets and cats, dogs and ferrets that people brought to penguin coasts.

Words to know

• fossil: old remains
• breed: raise young
• extinction: dying out
• illegal: against the law
• indicators: signs