The animal known to have the largest brain is the sperm whale (Physeter macrocephalus). An adult sperm whale's brain can weigh up to 9 kilograms (about 20 pounds), making it the largest brain of any known animal. Despite its impressive brain size, the intelligence of sperm whales is difficult to measure directly, as their complex social structures and behaviors in the wild present challenges. These magnificent marine mammals are known for their deep diving capabilities and social bonds. Understanding their behaviors and communication patterns contributes to research on cetacean intelligence and the complexities of marine ecosystems.