The animal with the longest pregnancy of any mammal is the elephant. Elephants, both African and Asian species, have notably long gestation periods. African elephants have a gestation period of approximately 22 months, while Asian elephants have a slightly shorter but still remarkable gestation period of around 18 to 22 months. This extended pregnancy allows for the development of the elephant calf, which is born relatively well-developed and ready to adapt to its environment, considering the challenges of being one of the world's largest land mammals.