The Internet of Things (IoT) has revolutionized the ways we monitor and ensure the safety and welfare of animals. Focusing on pets, livestock, and wildlife, this article provides an in-depth review of IoT-based solutions aimed at promoting animal well-being. We explore a wide range of IoT sensors and devices that track health, activity, and environmental conditions, enabling early detection of stress, illness, and potential safety risks. Additionally, IoT-enabled tools for monitoring animal location, movement, and social interactions are examined. The article also discusses how machine learning and data analytics can process IoT data to inform animal care decisions. Highlighted are successful IoT applications in animal welfare, including smart veterinary care, wildlife conservation, and precision livestock management.