What is the biggest fish in the world?

The biggest fish in the world is the whale shark (Rhincodon typus). Despite its enormous size, the whale shark is a harmless filter feeder that mainly eats plankton and small fish. A whale is not actually a fish at all but a marine mammal, so the title of biggest fish belongs to the whale shark instead.

Whale sharks can grow to more than 12 meters long and weigh over 20 tons, making them by far the largest fish species alive today. They live in warm tropical and subtropical oceans around the world and are considered an endangered species, threatened mainly by accidental capture in fishing gear and boat strikes.