Which animal has the largest population on Earth?

The animal with the largest population on Earth is the domestic chicken, with an estimated population of over 25 billion. Domestic chickens are the most widespread bird species and are found on every continent. They are a primary source of protein for humans and are kept for both meat and eggs.

Other animals with large populations include the house mouse, with an estimated population of over 1 billion, and the common rat, with an estimated population of over 500 million. In the wild, the red-billed quelea, a small bird found in Africa, has the largest population, estimated to be over 1.5 billion individuals.