Object permanence is a term used in child development to describe the comprehension of continued existence. A child that has achieved object permanence realizes that just because they cannot see, hear, or touch an item it still exists. A child that has not achieved it will think an item has ceased to exist when it cannot be empirically experienced. Many infants cry when their mother leaves possibly because they think she has ceased to exist.

Jean Piaget theorized object permanence around 1952. Only children of an infantile age have yet to achieve it. This milestone as a substage of the sensorimotor stage of child development signifies an important progression in the earliest stages of mental development. The way Piaget first tested for object permanence was to place an item in front of the child and then block it from the child's view. If the child would start to search for the now hidden item it signified some level of object permanence.