An emotional bond between an infant or animal and its caregiver, contributing to the infant or animal's experience of safety, comfort, and security while in the caregiver's presence and distress when temporarily separated.

Many developmental psychologists view attachment—the special relationship between infant and care-giver—as an important building block for later relationships and adult personality. Since attachment plays a central role in theories of social and emotional development, the scientific study of attachment has remained in the forefront of developmental psychology for the past several decades.