What animal has the shortest gestation period?

The shortest gestation period known is 12 to 13 days, shared by three marsupials: the American or Virginian opossum (Didelphis marsupialis); the rare water opossum, or yapok (Chironectes minimus) of central and northern South America; and the eastern native cat (Dasyurus viverrinus) of Australia.

Gestation is the period of time between fertilization and birth in oviparous animals.

The elephant has the longest gestation period of about 23 months of any land animal.