What mammal has the longest gestation period?

The African elephant has the longest gestation period of any mammal, lasting about 22 months. This unusually long pregnancy gives the developing calf time to form the large brain, strong skeleton, and coordination needed for life in a complex herd.

African elephants are the largest living land animals, and their calves are born weighing roughly 100 kilograms. Newborns can stand and walk soon after birth, an important survival advantage because the herd must keep moving and protect its young from predators.

The Asian elephant also has a very long pregnancy, generally around 18 to 22 months, which causes occasional confusion. However, African elephants are conventionally recognized as having the longest mammalian gestation. “Whale” is too broad to be a single species-level answer, since different whale species have different gestation lengths.

Elephant calves are raised within a strongly social herd, and females may spend years caring for and learning from them before the next calf arrives.