The largest mouth in the world belongs to the bowhead whale (Balaena mysticetus) and can measure 5 m (16 ft) long, 4 m (12 ft) high and 2.5 m (8 ft) wide. Its tongue weighs approximately one ton (900 kg).
Bowheads are mainly found near the Arctic icepack and feed on planktonic organisms consuming about two tons (1,814 kg) of food every day. As a baleen whale, the bowhead has between 325-360 fringed overlapping plates hanging from each side of the upper jaw, where teeth would normally be found. In fact, the bowhead has the longest baleen of any whale. While feeding, the whale opens its mouth and skims through the water. As the water flows through the mouth and through the baleen, the plankton get trapped inside near the tongue and are then swallowed.
Comments below may relate to previous holders of this record.