The largest animal in the ocean is the blue whale (Balaenoptera musculus). These majestic creatures can reach lengths of up to 100 feet (30 meters) and can weigh as much as 200 tons (approximately 181 metric tonnes), making them the largest animals ever known to exist on Earth. Blue whales primarily feed on tiny shrimp-like creatures called krill, consuming up to 4 tons of them each day during feeding season. Their immense size and unique vocalizations make them fascinating subjects of interest for marine biologists and conservationists, highlighting the importance of ocean ecosystems.