The oral stage is the initial phase of Sigmund Freud's theory of psychosexual development, occurring from birth to approximately 12 to 18 months. During this period, the infant's mouth serves as the primary source of pleasure, with actions such as sucking, chewing, biting, and drinking playing a crucial role in reducing tension. These activities are essential not only for nourishment but also for the infant's psychological and emotional satisfaction.

Weaning, typically occurring around the age of one year, marks a significant transition for the infant. Freud emphasized that improper handling of this process could lead to conflict. If unresolved, these conflicts may result in what he termed "oral fixation." Adults with oral fixation often exhibit behaviors such as smoking, overeating, nail-biting, or excessive drinking. These habits are seen as attempts to alleviate anxiety, reflecting unmet needs from the oral stage of development.

Freud also proposed that individuals with oral fixation might regress to infant-like behaviors when faced with stress. This regression is characterized by an increased dependence on others for reassurance, similar to the way an infant seeks comfort from its mother. The recurrence of behaviors reminiscent of early oral gratification suggests that unresolved psychological conflicts from infancy can persist into adulthood. Freud's theory links these behavioral patterns to unmet emotional and psychological needs from the earliest stages of life, illustrating the lasting impact of early development on personality and behavior.