Friendship plays a critical role in well-being across the lifespan, making it important to understand the dissolution of these relationships. Friendships end in many ways and for many reasons, which may result in different social and emotional outcomes. In this review, we examine the rapidly burgeoning literature on friendship dissolution from childhood through young adulthood, detailing current understanding of how common friendship dissolution is, as well as why and how it occurs. Research has documented that during childhood and adolescence, friendships are markedly unstable, although little work has examined friendship stability in adulthood. Characteristics of individuals (e.g., behavior, interpersonal cognition), friendships (e.g., homophily, quality), and the contexts in which friendships are embedded (e.g., friends' broader social networks) have all been linked to friendship stability. We document the diversity of ways in which friendships end, highlighting differences in timing, communication, and intent. Finally, we discuss circumstances under which dissolving a friendship may be helpful versus harmful. Future work should focus on elucidating friendship processes - that is, the positive and negative interactions that occur between friends - that contribute to dissolution, as well as developing interventions that promote the development and maintenance of high-quality friendships. Other critical research agendas are understanding friendship maintenance and dissolution among youth and young adults from marginalized groups and elucidating the ways in which technology may both strengthen and weaken friendships.