No, sharks are not mammals. They are actually a type of fish called elasmobranchs, which are cartilaginous fish. This means that they have skeletons made of cartilage rather than bone. Unlike mammals, sharks do not give birth to live young or nurse their young with milk. Instead, they lay eggs or give birth to live young that are already fully developed. While they may look similar to mammals in some ways, sharks are very different in terms of their anatomy and life cycle. So, while sharks are amazing and fascinating creatures, they are not mammals.