What is the biggest food chain in the world?

The "biggest" food chain in the world is found in the ocean. This marine food web is the largest and most complex network of feeding relationships on Earth.

The foundation of this massive system is phytoplankton. These are microscopic, plant-like organisms that float in the ocean and produce their own food through photosynthesis. They are the producers for almost all life in the sea.

A classic example of a long and significant food chain in the ocean is: Phytoplankton → Zooplankton (tiny animals) → Small Fish & Crustaceans → Larger Fish (like Mackerel or Herring) → Seals → Orca (Killer Whale)

However, if "biggest" refers to the food chain involving the largest animal on Earth, that would be the blue whale's food chain: Phytoplankton → Krill (a type of zooplankton) → Blue Whale

Even though this chain is short, the blue whale is the largest animal known to have ever existed, and it survives by eating enormous quantities of tiny krill.

Ultimately, the entire oceanic food web, with its countless interconnected chains, is considered the biggest food system in the world.