Youth development or "adolescent development" is the process through which adolescents (alternately called youth or young adults) acquire the cognitive, social, and emotional skills and abilities required to navigate life. The experience of adolescence varies for every youth: culture, gender, and socioeconomic class are important influences on development. This development occurs throughout a young person's life, including formal and informal settings such as home, church, or school; and similar relationships, such as peer friendships, work, parenting, teaching, or mentoring.

Youth is an important developmental period described in, most psychological theories of human development from Sigmund Freud's theory of psychosexual development, Carl Jung, and in particular Erik Erikson (see his stages of psychosocial development where adolescence is a time of identity formation).

During each stage, behavior changes in response to biological maturation and changes in the social environment. The process of entering adulthood entails many decisions both conscious and not. The examination of this stage of life is rooted in the child development theories of John Dewey, Jean Piaget, and Erik Erikson. Anthropologist Margaret Mead also added a great deal of understanding to this field. Regarding the successive evolution of youth as a social phenomenon, Mead reportedly wrote,

"As long as any adult thinks that he, like the parents and teachers of old, can become introspective, invoking his own youth to understand the youth before him, he is lost."

Recent important studies in the field of youth development have been led by organizations such as the Forum for Youth Investment and by the Innovation Center, both American nonprofit organizations.

The sociological field of study that examines youth development is separated into myriad political examinations of young people, including positive youth development and community youth development. Each of these entails particular connotations of the particular relevance or importance of young people to their families, schools, and communities.