Fifteen years ago, Jeffrey Jensen Arnett proposed emerging adulthood as a new life stage at ages 18-29, one distinct from both the adolescence that precedes it and the young adulthood that eventually follows. Rather than marrying and becoming parents in their early 20s, most people in developed countries now postpone these transitions until at least their late 20s, spending these years in self-focused explorations as they try out different possibilities in their education, careers, and relationships. Since Arnett proposed his theory of emerging adulthood in 2000, it has turned into a full-fledged academic field, and the ideas have been applied in practical areas as well, such as mental health and education. The Oxford Handbook of Emerging Adulthood brings together for the first time the wealth of theory and research that has developed in this new and burgeoning field. It includes chapters by many prominent scholars on a wide range of topics, such as brain development, relations with friends, relations with parents, expectations for marriage, sexual relationships, media use, substance use and abuse, and resilience. The chapters both summarize the existing research and point the way to new prospects for research in the years to come.